R - How to avoid loop in list of files -


my current learning goal in r avoid for loops. have list files in directory (or loops through directories) perform diverse operations on files.

one example of task following: have invoke system application called cdo merge 2 files. syntax of command is, let's say: cdo merge input_file1 input_file2 output_file.

my current r code looks this:

# set lists of files u.files <- c("uas_amon_access1-3.nc", "uas_amon_cmcc-cesm.nc", "uas_amon_cmcc-cesm.nc") v.files <- c("vas_amon_access1-3.nc", "vas_amon_cmcc-cesm.nc", "vas_amon_cmcc-cesm.nc")  (i in 1:length(u.files)) {    # set input file 1 use on cdo   input1 <- paste(u.files[i], sep='')    # set input file 2 use on cdo   input2 <- paste(v.files[i], sep='')    # set output file use on cdo   output <- paste('output_', u.files[i], sep='')     # assemble command string    comm <- paste('cdo merge', input1, input2, output, collapse='')    # submit command   system(comm)  }

which works ok although not good.

however, times hear people saying for loops in r slow , should avoided as possible.

is there way avoid loops , make code more efficient/legible in cases this?

this more r-idiomatic:

u.files <- c("uas_amon_access1-3.nc", "uas_amon_cmcc-cesm.nc", "uas_amon_cmcc-cesm.nc") v.files <- c("vas_amon_access1-3.nc", "vas_amon_cmcc-cesm.nc", "vas_amon_cmcc-cesm.nc") output <- paste('output_', u.files, sep='') comm <- paste('cdo merge', u.files, v.files, output) lapply(comm,system)

remember functions vectorized in r, don't have call paste each iteration in loop. @ end obtain vector of commands , execute 1 one through lapply in last line.


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