Streamflow
Streamflow values are stored as m^3/s. For plots and tables that
display discharge data, there is a user-argument to the functions called
qUnit. This input can be a numeric between 1 and 4, or it
can be one of the following text: “cfs”, “cms”, “thousandCfs”, or
“thousandCms”. The numeric that lines up with the text can be seen with
the printqUnitCheatSheet function:
## The following codes apply to the qUnit list:
## 1 = cfs ( Cubic Feet per Second )
## 2 = cms ( Cubic Meters per Second )
## 3 = thousandCfs ( Thousand Cubic Feet per Second )
## 4 = thousandCms ( Thousand Cubic Meters per Second )Here is an example of using the default (qUnit = 2 which
corresonds to “cms”), compared to using qUnit = 1
(corresponding to “cfs”):
Plots of discharge with different units.
Custom Units
There could be a scenario where EGRET analysis is not
done using a streamflow value. For example, let’s say we want to use
precipitation as a substitution for discharge. A very important point
here is that if you use data that are not designed for the
EGRET software, it will probably not make sense to use the
flux calculations. But, there are places where EGRET graphs
and tables will be interesting using this alternative data.
Here is an example of how to make a custom qUnit object.
It is not as simple as adding a single line of text. This is because the
software needs to know how to create nice labels for a variety of
different kind of plots, and if there is a conversion factor, it would
need to know that conversion factor. This example shows how to make a
custom qUnit for precipitation with millimeters as the
unit:
qConst_precip <- new("qUnit",
qShortName = " mm ",
qUnitFactor = 1,
qUnitName = "Millimeter",
qUnitExpress = expression(paste("Precipitation in ",mm)),
qUnitTiny = expression(paste("Precipitation ", "(", mm, ")")),
shortCode = 1,
unitUSGS = "Precipitation, in mm",
prefix = "Precipitation")Each “slot” in this qUnit object is required, and the
qShortName, qUnitName, unitUSGS, and prefix must be characters. The
qUnitFactor must be a numeric (this would be the conversion factor that
the data gets multiplied by). qUnitExpress and qUnitTiny are
“expressions” which allows the text to be formatted. To use this custom
unit:
Plot with custom axis, using precipitation instead of discharge.
Data input
Discharge data in units other than m^3/s can be used as input in
EGRET, but that data will be converted to m^3/s with the qUnit argument
when the eList is created. So if you have data that is coming in that is
in cubic feet per second, you could use the readDailyUser
function, and specify qUnit = 1. This will take your cfs
data, and store it properly as cms.
