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The goal of deflist is to provide a list-like object for
which element access is routed through a user-supplied function. This
can be used, for example, when list-like syntax is required but one
cannot afford to hold all elements in memory at once.
You can install the released version of deflist from CRAN with:
install.packages("deflist")And the development version from GitHub with:
# install.packages("devtools")
devtools::install_github("bbuchsbaum/deflist")
library(deflist)
dl <- deflist(function(i) i, len=10)
print(dl[[1]])
#> [1] 1
dl2 <- deflist(function(i) { Sys.sleep(5); i*2 }, len=10)
for (i in 1:10) {
print(dl2[[i]])
}
#> [1] 2
#> [1] 4
#> [1] 6
#> [1] 8
#> [1] 10
#> [1] 12
#> [1] 14
#> [1] 16
#> [1] 18
#> [1] 20The value at an index may change across calls, for example:
dl3 <- deflist(function(i) { rnorm(1) }, len=10)
print(dl3[[1]])
#> [1] 0.3200255
print(dl3[[1]])
#> [1] 0.3937322Memoisation can be enabled so that values at a given index are cached:
dl4 <- deflist(function(i) { rnorm(1) }, len=10, memoise=TRUE)
print(dl4[[1]])
#> [1] 0.1447534
print(dl4[[1]])
#> [1] 0.1447534In addition, memoisation can be set to store cached values to the file system:
dl5 <- deflist(function(i) { rnorm(1000) }, len=10, memoise=TRUE, cache="file", cachedir = tempdir())
print(dl5[[1]][1:10])
#> [1] 0.23399448 0.93722807 -0.34288042 0.36736236 0.87024915 -0.86566821
#> [7] 1.57174277 -0.38036486 -0.04497923 -0.34889371
print(dl5[[1]][1:10])
#> [1] 0.23399448 0.93722807 -0.34288042 0.36736236 0.87024915 -0.86566821
#> [7] 1.57174277 -0.38036486 -0.04497923 -0.34889371These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.