Question

If I have an R script:

#! /usr/bin/env Rscript
args <- commandArgs(TRUE)

t <- read.table(args[2], header = TRUE)
print(t$args[1])

q(status = 0)

which I use with the TSV file “example-table.tsv”:

"a" "b"
1 3
2 2
3 1

…using the Bash command: ./example.R a example-table.tsv… (after making the R script executable, of course)

Why does t$args[1] return NULL? How do I get this example to return the proper data.frame column that I specify in the script arguments?

Thanks for you help!

I realize this may or may not be a better question for programming, rather than Cross Validated…?

Answer 1

try:

print(t[[args[1]]])

note that t$args[1] is parsed as (t$args)[1] -> NULL[1] -> NULL because your data.frame has no ‘args’ column.