# Data Transformation

#### Choonghyun Ryu

#### 2025-08-24

## Preface

After you have acquired the data, you should do the following:

- Diagnose data quality.
  - If there is a problem with data quality,
  - The data must be corrected or re-acquired.
- Explore data to understand the data and find scenarios for performing the analysis.
- Derive new variables or perform variable transformations.

The dlookr package makes these steps fast and easy:

- Performs a data diagnosis or automatically generates a data diagnosis report.
- Discover data in various ways and automatically generate EDA(exploratory data analysis) reports.
- Impute missing values and outliers, resolve skewed data, and categorize continuous variables into categorical variables. And generates an automated report to support it.

This document introduces data transformation methods provided by the dlookr package. You will learn how to transform `tbl_df` data that inherits from data.frame and `data.frame` with functions provided by dlookr

dlookr increases synergy with `dplyr`. Particularly in data transformation and data wrangle, it increases the efficiency of the `tidyverse` package group.

## datasets

To illustrate the primary use of data transformation in the dlookr package, I use a `Carseats` dataset. `Carseats` in the `ISLR` package is simulation dataset that sells children’s car seats at 400 stores. This data is a data.frame created for the purpose of predicting sales volume.

    str(Carseats)
    'data.frame':   400 obs. of  11 variables:
     $ Sales      : num  9.5 11.22 10.06 7.4 4.15 ...
     $ CompPrice  : num  138 111 113 117 141 124 115 136 132 132 ...
     $ Income     : num  73 48 35 100 64 113 105 81 110 113 ...
     $ Advertising: num  11 16 10 4 3 13 0 15 0 0 ...
     $ Population : num  276 260 269 466 340 501 45 425 108 131 ...
     $ Price      : num  120 83 80 97 128 72 108 120 124 124 ...
     $ ShelveLoc  : Factor w/ 3 levels "Bad","Good","Medium": 1 2 3 3 1 1 3 2 3 3 ...
     $ Age        : num  42 65 59 55 38 78 71 67 76 76 ...
     $ Education  : num  17 10 12 14 13 16 15 10 10 17 ...
     $ Urban      : Factor w/ 2 levels "No","Yes": 2 2 2 2 2 1 2 2 1 1 ...
     $ US         : Factor w/ 2 levels "No","Yes": 2 2 2 2 1 2 1 2 1 2 ...

The contents of individual variables are as follows. (Refer to ISLR::Carseats Man page)

- Sales
  - Unit sales (in thousands) at each location
- CompPrice
  - Price charged by a competitor at each location
- Income
  - Community income level (in thousands of dollars)
- Advertising
  - Local advertising budget for company at each location (in thousands of dollars)
- Population
  - Population size in region (in thousands)
- Price
  - Price company charges for car seats at each site
- ShelveLoc
  - A factor with levels Bad, Good and Medium indicating the quality of the shelving location for the car seats at each site
- Age
  - Average age of the local population
- Education
  - Education level at each location
- Urban
  - A factor with levels No and Yes to indicate whether the store is in an urban or rural location
- US
  - A factor with levels No and Yes to indicate whether the store is in the US or not

When data analysis is performed, data containing missing values is often encountered. However, `Carseats` is complete data without missing. Therefore, the missing values are generated as follows. And I created a data.frame object named carseat.

    carseats <- Carseats

    suppressWarnings(RNGversion("3.5.0"))
    set.seed(123)
    carseats[sample(seq(NROW(carseats)), 20), "Income"] <- NA

    suppressWarnings(RNGversion("3.5.0"))
    set.seed(456)
    carseats[sample(seq(NROW(carseats)), 10), "Urban"] <- NA

## Data Transformation

dlookr imputes missing values and outliers and resolves skewed data. It also provides the ability to bin continuous variables as categorical variables.

Here is a list of the data conversion functions and functions provided by dlookr:

- `find_na()` finds a variable that contains the missing values variable, and `imputate_na()` imputes the missing values.
- `find_outliers()` finds a variable that contains the outliers, and `imputate_outlier()` imputes the outlier.
- `summary.imputation()` and `plot.imputation()` provide information and visualization of the imputed variables.
- `find_skewness()` finds the variables of the skewed data, and `transform()` resolves the skewed data.
- `transform()` also performs standardization of numeric variables.
- `summary.transform()` and `plot.transform()` provide information and visualization of transformed variables.
- `binning()` and `binning_by()` convert binational data into categorical data.
- `print.bins()` and `summary.bins()` show and summarize the binning results.
- `plot.bins()` and `plot.optimal_bins()` provide visualization of the binning result.
- `transformation_report()` performs the data transform and reports the result.

## Imputation of missing values

### imputes the missing value with `imputate_na()`

`imputate_na()` imputes the missing value contained in the variable. The predictor with missing values supports numeric and categorical variables and the following `method`.

- predictor is numerical variable
  - “mean”: arithmetic mean
  - “median”: median
  - “mode”: mode
  - “knn”: K-nearest neighbors
    - target variable must be specified
  - “rpart”: Recursive Partitioning and Regression Trees
    - target variable must be specified
  - “mice”: Multivariate Imputation by Chained Equations
    - target variable must be specified
    - random seed must be set
- predictor is categorical variable
  - “mode”: mode
  - “rpart”: Recursive Partitioning and Regression Trees
    - target variable must be specified
  - “mice”: Multivariate Imputation by Chained Equations
    - target variable must be specified
    - random seed must be set

In the following example, `imputate_na()` imputes the missing value of `Income`, a numeric variable of carseats, using the “rpart” method. `summary()` summarizes missing value imputation information, and `plot()` visualizes missing information.

    if (requireNamespace("rpart", quietly = TRUE)) {
      income <- imputate_na(carseats, Income, US, method = "rpart")

      # result of imputation
      income

      # summary of imputation
      summary(income)

      # viz of imputation
      plot(income)
    } else {
      cat("If you want to use this feature, you need to install the rpart package.\n")
    }
    * Impute missing values based on Recursive Partitioning and Regression Trees
     - method : rpart

    * Information of Imputation (before vs after)
                        Original     Imputation
    described_variables "value"      "value"
    n                   "380"        "400"
    na                  "20"         " 0"
    mean                "68.86053"   "69.05073"
    sd                  "28.09161"   "27.57382"
    se_mean             "1.441069"   "1.378691"
    IQR                 "48.25"      "46.00"
    skewness            "0.04490600" "0.02935732"
    kurtosis            "-1.089201"  "-1.035086"
    p00                 "21"         "21"
    p01                 "21.79"      "21.99"
    p05                 "26"         "26"
    p10                 "30.0"       "30.9"
    p20                 "39"         "40"
    p25                 "42.75"      "44.00"
    p30                 "48.00000"   "51.58333"
    p40                 "62"         "63"
    p50                 "69"         "69"
    p60                 "78.0"       "77.4"
    p70                 "86.3"       "84.3"
    p75                 "91"         "90"
    p80                 "96.2"       "96.0"
    p90                 "108.1"      "106.1"
    p95                 "115.05"     "115.00"
    p99                 "119.21"     "119.01"
    p100                "120"        "120"

The following imputes the categorical variable `urban` by the “mice” method.

The “mice” method must require the `mice`, `ranger` package. If you want to use this feature, you need to install the `mice`, and `ranger` package.

    library(mice)

    urban <- imputate_na(carseats, Urban, US, method = "mice")

    # result of imputation
    urban

    # summary of imputation
    summary(urban)

    # viz of imputation
    plot(urban)

### Collaboration with dplyr

The following example imputes the missing value of the `Income` variable and then calculates the arithmetic mean for each level of `US`. In this case, `dplyr` is used and is easily interpreted logically using pipes.

    # The mean before and after the imputation of the Income variable
    carseats %>%
      mutate(Income_imp = imputate_na(carseats, Income, US, method = "knn")) %>%
      group_by(US) %>%
      summarise(orig = mean(Income, na.rm = TRUE),
                imputation = mean(Income_imp))
    # A tibble: 2 × 3
      US     orig imputation
      <fct> <dbl>      <dbl>
    1 No     65.8       66.1
    2 Yes    70.4       70.5

## Impute outliers

### imputes the outliers with `imputate_outlier()`

`imputate_outlier()` imputes the outlier value. The predictor with outliers supports only numeric variables and supports the following methods.

- predictor is numerical variable
  - “mean”: arithmetic mean
  - “median”: median
  - “mode”: mode
  - “capping”: Impute the upper outliers with the 95 percentile and the bottom outliers with the fifth percentile.

`imputate_outlier()` imputes the outliers with the numeric variable `Price` as the “capping” method, as follows. `summary()` summarizes outliers imputation information, and `plot()` visualizes imputation information.

    price <- imputate_outlier(carseats, Price, method = "capping")

    # result of imputation
    price
      [1] 120.00  83.00  80.00  97.00 128.00  72.00 108.00 120.00 124.00 124.00
     [11] 100.00  94.00 136.00  86.00 118.00 144.00 110.00 131.00  68.00 121.00
     [21] 131.00 109.00 138.00 109.00 113.00  82.00 131.00 107.00  97.00 102.00
     [31]  89.00 131.00 137.00 128.00 128.00  96.00 100.00 110.00 102.00 138.00
     [41] 126.00 124.00  77.00 134.00  95.00 135.00  70.00 108.00  98.00 149.00
     [51] 108.00 108.00 129.00 119.00 144.00 154.00  84.00 117.00 103.00 114.00
     [61] 123.00 107.00 133.00 101.00 104.00 128.00  91.00 115.00 134.00  99.00
     [71]  99.00 150.00 116.00 104.00 136.00  92.00  70.00  89.00 145.00  90.00
     [81]  79.00 128.00 139.00  94.00 121.00 112.00 134.00 126.00 111.00 119.00
     [91] 103.00 107.00 125.00 104.00  84.00 148.00 132.00 129.00 127.00 107.00
    [101] 106.00 118.00  97.00  96.00 138.00  97.00 139.00 108.00 103.00  90.00
    [111] 116.00 151.00 125.00 127.00 106.00 129.00 128.00 119.00  99.00 128.00
    [121] 131.00  87.00 108.00 155.00 120.00  77.00 133.00 116.00 126.00 147.00
    [131]  77.00  94.00 136.00  97.00 131.00 120.00 120.00 118.00 109.00  94.00
    [141] 129.00 131.00 104.00 159.00 123.00 117.00 131.00 119.00  97.00  87.00
    [151] 114.00 103.00 128.00 150.00 110.00  69.00 157.00  90.00 112.00  70.00
    [161] 111.00 160.00 149.00 106.00 141.00 155.05 137.00  93.00 117.00  77.00
    [171] 118.00  55.00 110.00 128.00 155.05 122.00 154.00  94.00  81.00 116.00
    [181] 149.00  91.00 140.00 102.00  97.00 107.00  86.00  96.00  90.00 104.00
    [191] 101.00 173.00  93.00  96.00 128.00 112.00 133.00 138.00 128.00 126.00
    [201] 146.00 134.00 130.00 157.00 124.00 132.00 160.00  97.00  64.00  90.00
    [211] 123.00 120.00 105.00 139.00 107.00 144.00 144.00 111.00 120.00 116.00
    [221] 124.00 107.00 145.00 125.00 141.00  82.00 122.00 101.00 163.00  72.00
    [231] 114.00 122.00 105.00 120.00 129.00 132.00 108.00 135.00 133.00 118.00
    [241] 121.00  94.00 135.00 110.00 100.00  88.00  90.00 151.00 101.00 117.00
    [251] 156.00 132.00 117.00 122.00 129.00  81.00 144.00 112.00  81.00 100.00
    [261] 101.00 118.00 132.00 115.00 159.00 129.00 112.00 112.00 105.00 166.00
    [271]  89.00 110.00  63.00  86.00 119.00 132.00 130.00 125.00 151.00 158.00
    [281] 145.00 105.00 154.00 117.00  96.00 131.00 113.00  72.00  97.00 156.00
    [291] 103.00  89.00  74.00  89.00  99.00 137.00 123.00 104.00 130.00  96.00
    [301]  99.00  87.00 110.00  99.00 134.00 132.00 133.00 120.00 126.00  80.00
    [311] 166.00 132.00 135.00  54.00 129.00 171.00  72.00 136.00 130.00 129.00
    [321] 152.00  98.00 139.00 103.00 150.00 104.00 122.00 104.00 111.00  89.00
    [331] 112.00 134.00 104.00 147.00  83.00 110.00 143.00 102.00 101.00 126.00
    [341]  91.00  93.00 118.00 121.00 126.00 149.00 125.00 112.00 107.00  96.00
    [351]  91.00 105.00 122.00  92.00 145.00 146.00 164.00  72.00 118.00 130.00
    [361] 114.00 104.00 110.00 108.00 131.00 162.00 134.00  77.00  79.00 122.00
    [371] 119.00 126.00  98.00 116.00 118.00 124.00  92.00 125.00 119.00 107.00
    [381]  89.00 151.00 121.00  68.00 112.00 132.00 160.00 115.00  78.00 107.00
    [391] 111.00 124.00 130.00 120.00 139.00 128.00 120.00 159.00  95.00 120.00
    attr(,"method")
    [1] "capping"
    attr(,"var_type")
    [1] "numerical"
    attr(,"outlier_pos")
    [1]  43 126 166 175 368
    attr(,"outliers")
    [1]  24  49 191 185  53
    attr(,"type")
    [1] "outliers"
    attr(,"message")
    [1] "complete imputation"
    attr(,"success")
    [1] TRUE
    attr(,"class")
    [1] "imputation" "numeric"

    # summary of imputation
    summary(price)
    Impute outliers with capping

    * Information of Imputation (before vs after)
                        Original     Imputation
    described_variables "value"      "value"
    n                   "400"        "400"
    na                  "0"          "0"
    mean                "115.7950"   "115.8927"
    sd                  "23.67666"   "22.61092"
    se_mean             "1.183833"   "1.130546"
    IQR                 "31"         "31"
    skewness            "-0.1252862" "-0.0461621"
    kurtosis            " 0.4518850" "-0.3030578"
    p00                 "24"         "54"
    p01                 "54.99"      "67.96"
    p05                 "77"         "77"
    p10                 "87"         "87"
    p20                 "96.8"       "96.8"
    p25                 "100"        "100"
    p30                 "104"        "104"
    p40                 "110"        "110"
    p50                 "117"        "117"
    p60                 "122"        "122"
    p70                 "128.3"      "128.3"
    p75                 "131"        "131"
    p80                 "134"        "134"
    p90                 "146"        "146"
    p95                 "155.0500"   "155.0025"
    p99                 "166.05"     "164.02"
    p100                "191"        "173"

    # viz of imputation
    plot(price)

### Collaboration with dplyr

The following example imputes the outliers of the `Price` variable and then calculates the arithmetic mean for each level of `US`. In this case, `dplyr` is used and is easily interpreted logically using pipes.

    # The mean before and after the imputation of the Price variable
    carseats %>%
      mutate(Price_imp = imputate_outlier(carseats, Price, method = "capping")) %>%
      group_by(US) %>%
      summarise(orig = mean(Price, na.rm = TRUE),
        imputation = mean(Price_imp, na.rm = TRUE))
    # A tibble: 2 × 3
      US     orig imputation
      <fct> <dbl>      <dbl>
    1 No     114.       114.
    2 Yes    117.       117.

## Standardization and Resolving Skewness

### Introduction to the use of `transform()`

`transform()` performs data transformation. Only numeric variables are supported, and the following methods are provided.

- Standardization
  - “zscore”: z-score transformation. (x - mu) / sigma
  - “minmax”: minmax transformation. (x - min) / (max - min)
- Resolving Skewness
  - “log”: log transformation. log(x)
  - “log+1”: log transformation. log(x + 1). Used for values that contain 0.
  - “sqrt”: square root transformation.
  - “1/x”: 1 / x transformation
  - “x^2”: x square transformation
  - “x^3”: x^3 square transformation

### Standardization with `transform()`

Use the methods “zscore” and “minmax” to perform standardization.

    carseats %>%
      mutate(Income_minmax = transform(carseats$Income, method = "minmax"),
        Sales_minmax = transform(carseats$Sales, method = "minmax")) %>%
      select(Income_minmax, Sales_minmax) %>%
      boxplot()

### Resolving Skewness data with `transform()`

`find_skewness()` searches for variables with skewed data. This function finds data skewed by search conditions and calculates skewness.

    # find index of skewed variables
    find_skewness(carseats)
    [1] 4

    # find names of skewed variables
    find_skewness(carseats, index = FALSE)
    [1] "Advertising"

    # compute the skewness
    find_skewness(carseats, value = TRUE)
          Sales   CompPrice      Income Advertising  Population       Price
          0.185      -0.043       0.045       0.637      -0.051      -0.125
            Age   Education
         -0.077       0.044

    # compute the skewness & filtering with threshold
    find_skewness(carseats, value = TRUE, thres = 0.1)
          Sales Advertising       Price
          0.185       0.637      -0.125

The skewness of `Advertising` is 0.637. This means that the distribution of data is somewhat inclined to the left. So, for normal distribution, use `transform()` to convert to the “log” method as follows. `summary()` summarizes transformation information, and `plot()` visualizes transformation information.

    Advertising_log <- transform(carseats$Advertising, method = "log")

    # result of transformation
    head(Advertising_log)
    [1] 2.397895 2.772589 2.302585 1.386294 1.098612 2.564949
    # summary of transformation
    summary(Advertising_log)
    * Resolving Skewness with log

    * Information of Transformation (before vs after)
                Original Transformation
    n        400.0000000    400.0000000
    na         0.0000000      0.0000000
    mean       6.6350000           -Inf
    sd         6.6503642            NaN
    se_mean    0.3325182            NaN
    IQR       12.0000000            Inf
    skewness   0.6395858            NaN
    kurtosis  -0.5451178            NaN
    p00        0.0000000           -Inf
    p01        0.0000000           -Inf
    p05        0.0000000           -Inf
    p10        0.0000000           -Inf
    p20        0.0000000           -Inf
    p25        0.0000000           -Inf
    p30        0.0000000           -Inf
    p40        2.0000000      0.6931472
    p50        5.0000000      1.6094379
    p60        8.4000000      2.1265548
    p70       11.0000000      2.3978953
    p75       12.0000000      2.4849066
    p80       13.0000000      2.5649494
    p90       16.0000000      2.7725887
    p95       19.0000000      2.9444390
    p99       23.0100000      3.1359198
    p100      29.0000000      3.3672958
    # viz of transformation
    plot(Advertising_log)

The raw data seems to contain 0, as there is a -Inf in the log converted value. So this time, convert it to “log+1”.

    Advertising_log <- transform(carseats$Advertising, method = "log+1")

    # result of transformation
    head(Advertising_log)
    [1] 2.484907 2.833213 2.397895 1.609438 1.386294 2.639057
    # summary of transformation
    summary(Advertising_log)
    * Resolving Skewness with log+1

    * Information of Transformation (before vs after)
                Original Transformation
    n        400.0000000   400.00000000
    na         0.0000000     0.00000000
    mean       6.6350000     1.46247709
    sd         6.6503642     1.19436323
    se_mean    0.3325182     0.05971816
    IQR       12.0000000     2.56494936
    skewness   0.6395858    -0.19852549
    kurtosis  -0.5451178    -1.66342876
    p00        0.0000000     0.00000000
    p01        0.0000000     0.00000000
    p05        0.0000000     0.00000000
    p10        0.0000000     0.00000000
    p20        0.0000000     0.00000000
    p25        0.0000000     0.00000000
    p30        0.0000000     0.00000000
    p40        2.0000000     1.09861229
    p50        5.0000000     1.79175947
    p60        8.4000000     2.23936878
    p70       11.0000000     2.48490665
    p75       12.0000000     2.56494936
    p80       13.0000000     2.63905733
    p90       16.0000000     2.83321334
    p95       19.0000000     2.99573227
    p99       23.0100000     3.17846205
    p100      29.0000000     3.40119738
    # viz of transformation
    # plot(Advertising_log)

## Binning

### Binning of individual variables using `binning()`

`binning()` transforms a numeric variable into a categorical variable by binning it. The following types of binning are supported.

- “quantile”: categorize using quantile to include the same frequencies
- “equal”: categorize to have equal length segments
- “pretty”: categorized into moderately good segments
- “kmeans”: categorization using K-means clustering
- “bclust”: categorization using bagged clustering technique

Here are some examples of bin `Income` using `binning()`.

    # Binning the carat variable. the default type argument is "quantile"
    bin <- binning(carseats$Income)
    # Print bins class object
    bin
    binned type: quantile
    number of bins: 10
    x
            [21,30]         (30,39]         (39,48]         (48,62]         (62,69]
                 40              37              38              40              42
            (69,78]   (78,86.56667] (86.56667,96.6] (96.6,108.6333]  (108.6333,120]
                 33              36              38              38              38
               <NA>
                 20
    # Summarize bins class object
    summary(bin)
                levels freq   rate
    1          [21,30]   40 0.1000
    2          (30,39]   37 0.0925
    3          (39,48]   38 0.0950
    4          (48,62]   40 0.1000
    5          (62,69]   42 0.1050
    6          (69,78]   33 0.0825
    7    (78,86.56667]   36 0.0900
    8  (86.56667,96.6]   38 0.0950
    9  (96.6,108.6333]   38 0.0950
    10  (108.6333,120]   38 0.0950
    11            <NA>   20 0.0500
    # Plot bins class object
    plot(bin)
    Don't know how to automatically pick scale for object of type <table>.
    Defaulting to continuous.

    # Using labels argument
    bin <- binning(carseats$Income, nbins = 4,
                  labels = c("LQ1", "UQ1", "LQ3", "UQ3"))
    bin
    binned type: quantile
    number of bins: 4
    x
     LQ1  UQ1  LQ3  UQ3 <NA>
      95  102   89   94   20
    # Using another type argument
    binning(carseats$Income, nbins = 5, type = "equal")
    binned type: equal
    number of bins: 5
    x
       [21,40.8]  (40.8,60.6]  (60.6,80.4] (80.4,100.2]  (100.2,120]         <NA>
              81           65           94           80           60           20
    binning(carseats$Income, nbins = 5, type = "pretty")
    binned type: pretty
    number of bins: 5
    x
      [20,40]   (40,60]   (60,80]  (80,100] (100,120]      <NA>
           81        65        94        80        60        20

    if (requireNamespace("classInt", quietly = TRUE)) {
      binning(carseats$Income, nbins = 5, type = "kmeans")
      binning(carseats$Income, nbins = 5, type = "bclust")
    } else {
      cat("If you want to use this feature, you need to install the classInt package.\n")
    }
    binned type: bclust
    number of bins: 5
    x
         [21,49]    (49,64.5]  (64.5,86.5] (86.5,107.5]  (107.5,120]         <NA>
             115           52           99           75           39           20

    # Extract the binned results
    extract(bin)
      [1] LQ3  UQ1  LQ1  UQ3  UQ1  UQ3  UQ3  LQ3  UQ3  UQ3  LQ3  UQ3  LQ1  LQ1  UQ3
     [16] UQ3  <NA> <NA> UQ3  LQ3  LQ3  LQ1  UQ1  LQ1  UQ3  LQ1  UQ3  UQ3  LQ3  UQ3
     [31] UQ3  UQ1  LQ1  LQ1  UQ1  LQ3  LQ3  LQ1  LQ3  <NA> UQ3  UQ1  UQ1  LQ1  LQ3
     [46] UQ1  LQ3  UQ3  UQ1  UQ3  LQ1  LQ3  LQ1  UQ1  UQ3  LQ3  LQ3  LQ3  UQ3  LQ3
     [61] UQ3  LQ1  UQ1  LQ3  UQ1  LQ1  UQ3  UQ1  UQ1  UQ1  LQ3  UQ1  UQ1  LQ3  UQ1
     [76] UQ3  LQ3  LQ3  UQ1  UQ1  UQ3  LQ3  LQ3  LQ1  LQ1  UQ3  LQ3  UQ1  LQ1  UQ1
     [91] LQ1  UQ1  UQ3  LQ1  <NA> LQ1  LQ1  LQ3  LQ3  UQ1  UQ1  UQ3  LQ1  LQ3  UQ3
    [106] UQ3  LQ1  UQ3  LQ3  UQ1  UQ1  UQ3  UQ3  LQ1  LQ3  <NA> LQ3  UQ1  LQ3  UQ3
    [121] UQ3  LQ3  UQ3  UQ3  UQ3  <NA> UQ1  UQ1  UQ3  UQ3  LQ3  UQ1  LQ3  UQ3  LQ1
    [136] UQ3  LQ3  LQ1  UQ3  UQ1  UQ1  LQ1  LQ3  LQ3  UQ1  UQ1  LQ3  UQ1  UQ3  UQ3
    [151] LQ3  UQ1  LQ3  LQ1  UQ1  LQ3  LQ1  UQ1  LQ3  UQ1  LQ1  LQ1  <NA> UQ1  UQ1
    [166] UQ1  UQ1  LQ3  LQ3  LQ1  LQ1  UQ3  UQ3  LQ3  LQ1  LQ3  <NA> LQ3  <NA> LQ1
    [181] UQ3  LQ3  UQ1  LQ3  LQ1  UQ3  UQ1  LQ1  LQ1  UQ3  LQ1  LQ1  LQ1  LQ3  UQ3
    [196] UQ3  LQ1  UQ1  LQ3  LQ3  UQ3  LQ3  LQ3  LQ3  LQ3  LQ1  UQ1  UQ3  <NA> LQ1
    [211] LQ1  UQ3  UQ1  LQ3  UQ3  LQ3  <NA> UQ1  UQ1  LQ3  UQ3  <NA> UQ3  UQ1  LQ3
    [226] LQ1  LQ1  UQ1  LQ3  UQ3  UQ1  UQ1  LQ3  LQ3  UQ1  LQ1  LQ1  LQ1  LQ1  UQ3
    [241] LQ3  UQ1  UQ1  LQ1  LQ1  UQ1  UQ1  UQ3  UQ1  UQ1  UQ3  UQ3  UQ3  LQ1  UQ3
    [256] LQ3  LQ1  UQ1  LQ1  LQ1  UQ3  LQ1  <NA> LQ1  LQ1  LQ1  UQ3  LQ3  UQ1  UQ1
    [271] LQ1  UQ1  LQ1  UQ3  UQ3  UQ3  UQ1  UQ1  UQ3  UQ1  LQ3  UQ1  UQ3  UQ3  UQ1
    [286] LQ1  UQ3  UQ1  LQ1  LQ3  UQ3  LQ3  UQ1  LQ3  LQ3  LQ1  UQ1  LQ3  UQ1  LQ1
    [301] LQ3  UQ3  LQ3  UQ1  UQ3  LQ1  LQ1  UQ3  LQ3  UQ3  UQ1  UQ1  UQ3  LQ3  <NA>
    [316] LQ1  LQ1  LQ1  LQ3  UQ1  LQ3  LQ1  UQ1  UQ3  UQ1  UQ1  LQ1  LQ1  UQ1  UQ1
    [331] UQ1  UQ1  LQ1  UQ1  UQ3  LQ3  LQ1  LQ1  LQ1  UQ1  LQ1  UQ3  UQ3  LQ1  LQ3
    [346] UQ1  <NA> LQ1  UQ3  LQ1  <NA> UQ3  UQ3  UQ1  LQ1  UQ3  UQ3  LQ3  UQ3  UQ1
    [361] LQ3  LQ1  UQ1  <NA> LQ1  LQ1  UQ1  UQ3  LQ1  UQ3  LQ1  LQ3  <NA> <NA> UQ1
    [376] UQ1  UQ1  UQ1  LQ3  UQ3  UQ1  UQ1  LQ1  UQ3  LQ1  LQ3  UQ3  LQ3  LQ3  LQ1
    [391] LQ3  UQ1  LQ1  UQ1  UQ1  UQ3  <NA> LQ1  LQ3  LQ1
    Levels: LQ1 < UQ1 < LQ3 < UQ3

    # -------------------------
    # Using pipes & dplyr
    # -------------------------
    library(dplyr)

    carseats %>%
     mutate(Income_bin = binning(carseats$Income) %>%
                         extract()) %>%
     group_by(ShelveLoc, Income_bin) %>%
     summarise(freq = n()) %>%
     arrange(desc(freq)) %>%
     head(10)
    `summarise()` has grouped output by 'ShelveLoc'. You can override using the
    `.groups` argument.
    # A tibble: 10 × 3
    # Groups:   ShelveLoc [1]
      ShelveLoc Income_bin  freq
      <fct>     <ord>      <int>
    1 Medium    [21,30]       25
    2 Medium    (62,69]       24
    3 Medium    (48,62]       23
    4 Medium    (39,48]       21
    # ℹ 6 more rows

### Optimal Binning with `binning_by()`

`binning_by()` transforms a numeric variable into a categorical variable by optimal binning. This method is often used when developing a `scorecard model`.

The following `binning_by()` example optimally binning `Advertising` considering the target variable `US` with a binary class.

    library(dplyr)

    if (requireNamespace("partykit", quietly = TRUE)) {
      # optimal binning using character
      bin <- binning_by(carseats, "US", "Advertising")

      # optimal binning using name
      bin <- binning_by(carseats, US, Advertising)
      bin

      # summary optimal_bins class
      summary(bin)

      # performance table
      attr(bin, "performance")

      # visualize optimal_bins class
      plot(bin)

      # extract binned results
      extract(bin) %>%
        head(20)
    } else {
      cat("If you want to use this feature, you need to install the partykit package.\n")
    }
    Warning in binning_by(carseats, "US", "Advertising"): The factor y has been changed to a numeric vector consisting of 0 and 1.
    'Yes' changed to 1 (positive) and 'No' changed to 0 (negative).
    Warning in binning_by(carseats, US, Advertising): The factor y has been changed to a numeric vector consisting of 0 and 1.
    'Yes' changed to 1 (positive) and 'No' changed to 0 (negative).
    ── Binning Table ──────────────────────── Several Metrics ──
         Bin CntRec CntPos CntNeg RatePos RateNeg    Odds      WoE      IV     JSD
    1 [-1,0]    144     19    125 0.07364 0.88028  0.1520 -2.48101 2.00128 0.20093
    2  (0,6]     69     54     15 0.20930 0.10563  3.6000  0.68380 0.07089 0.00869
    3 (6,29]    187    185      2 0.71705 0.01408 92.5000  3.93008 2.76272 0.21861
    4  Total    400    258    142 1.00000 1.00000  1.8169       NA 4.83489 0.42823
          AUC
    1 0.03241
    2 0.01883
    3 0.00903
    4 0.06028

    ── General Metrics ─────────────────────────────────────────
    • Gini index                       :  -0.87944
    • IV (Jeffrey)                     :  4.83489
    • JS (Jensen-Shannon) Divergence   :  0.42823
    • Kolmogorov-Smirnov Statistics    :  0.80664
    • HHI (Herfindahl-Hirschman Index) :  0.37791
    • HHI (normalized)                 :  0.06687
    • Cramer's V                       :  0.81863

    ── Significance Tests ──────────────────── Chisquare Test ──
       Bin A  Bin B statistics      p_value
    1 [-1,0]  (0,6]   87.67064 7.731349e-21
    2  (0,6] (6,29]   34.73349 3.780706e-09

     [1] (6,29] (6,29] (6,29] (0,6]  (0,6]  (6,29] [-1,0] (6,29] [-1,0] [-1,0]
    [11] (6,29] (0,6]  (0,6]  (6,29] (6,29] (0,6]  [-1,0] (6,29] [-1,0] (6,29]
    Levels: [-1,0] < (0,6] < (6,29]

## Automated report

dlookr provides two automated data transformation reports:

- Web page-based dynamic reports can perform in-depth analysis through visualization and statistical tables.
- Static reports generated as pdf files or html files can be archived as output of data analysis.

### Create a dynamic report using `transformation_web_report()`

`transformation_web_report()` creates a dynamic report for objects inherited from data.frame(`tbl_df`, `tbl`, etc) or data.frame.

#### Contents of dynamic web report

The contents of the report are as follows.:

- Overview
  - Data Structures
  - Data Types
  - Job Informations
- Imputation
  - Missing Values
  - Outliers
- Resolving Skewness
- Binning
- Optimal Binning

#### Some arguments for dynamic web report

transformation_web_report() generates various reports with the following arguments.

- target
  - target variable
- output_file
  - name of the generated file.
- output_dir
  - name of the directory to generate report file.
- title
  - title of the report.
- subtitle
  - subtitle of the report.
- author
  - author of the report.
- title_color
  - color of title.
- logo_img
  - The name of the logo image file is on the top left.
- create_date
  - The date on which the report is generated.
- theme
  - name of the theme for the report. Support “orange” and “blue”.
- sample_percent
  - Sample percent of data for performing data transformation.

The following script creates a data transformation report for the `tbl_df` class object, `heartfailure`.

    heartfailure %>%
      transformation_web_report(target = "death_event", subtitle = "heartfailure",
                                output_dir = "./", output_file = "transformation.html",
                                theme = "blue")

#### Screenshot of dynamic report

- The dynamic contents of the report are shown in the following figure.:

The part of the report

### Create a static report using `transformation_paged_report()`

`transformation_paged_report()` create static report for object inherited from data.frame(`tbl_df`, `tbl`, etc) or data.frame.

#### Contents of static paged report

The contents of the report are as follows.:

- Overview
  - Data Structures
  - Job Informations
- Imputation
  - Missing Values
  - Outliers
- Resolving Skewness
- Binning
- Optimal Binning

#### Some arguments for static paged report

transformation_paged_report() generates various reports with the following arguments.

- target
  - target variable
- output_format
  - report output type. Choose either “pdf” or “html”.
- output_file
  - name of the generated file.
- output_dir
  - name of the directory to generate the report file.
- title
  - title of the report.
- subtitle
  - subtitle of the report.
- abstract_title
  - abstract of the report
- author
  - author of the report.
- title_color
  - color of title.
- subtitle_color
  - color of subtitle.
- logo_img
  - The name of the logo image file is on the top left.
- cover_img
  - name of cover image file on center.
- create_date
  - The date on which the report is generated.
- theme
  - name of the theme for the report. Support “orange” and “blue”.
- sample_percent
  - Sample percent of data for performing data transformation.

The following script creates a data transformation report for the `data.frame` class object, `heartfailure`.

    heartfailure %>%
      transformation_paged_report(target = "death_event", subtitle = "heartfailure",
                                  output_dir = "./", output_file = "transformation.pdf",
                                  theme = "blue")

#### Screenshot of static report

- The cover of the report is shown in the following figure.:

The part of the report

- The contents of the report are shown in the following figure.:

The dynamic contents of the report