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rrastersapplyrda

Why can't I use an apply function in R to load .rda files into the R workspace?

I have a list of .rda (RData) files. I would like to quickly load this data into R, without having to call the load function multiple times. I thought of using the load() function with sapply. However, using the following code, does not load any R objects in the workspace:

# List files    
gewataPath <- list.files(path = file.path(datdir), pattern = glob2rx('Gewata*.rda'), full.names = T)
# Load files
sapply(gewataPath, function(file) {load(file)})

Neither does it give any error.

Running a loop does load the .rda files into the R workspace as RasterLayer objects:

for (i in 1:length(gewataPath)) {
  load(gewataPath[i])
}

My question is: Why can't I use an apply() function to quickly load .rda files into the R workspace, and do I have to use a loop?

About the data: The data contains RasterLayers (from the Landsat satellite), located in Gewata, Ethiopia.

Solution

  • load() will load the data into the environment in which it was called. When you create function to pass to sapply, that function gets it's own environment. If you want the objects to exist after the sapply, you want to load the objects into the global environment, not the function environment. You can do that with the envir= parameter

    sapply(gewataPath, function(file) {load(file, envir=globalenv())})

    Or just

    sapply(gewataPath, load, envir=globalenv())