Subsetting columns by a string variable returns NULL in R

Question

I can subset a column named A from a data frame x_data using x_data$A. But if I do

some_string<-'A'
x_data$some_string

I get NULL. Can someone please explain why is it so. Thanks.

On the second line, R will only look for the symbol `some_string` within `x_data`. It doesn't matter whether you have a variable `some_string` defined in the global environment or not, as R won't look there. — Marius, Feb 05 '18 at 05:57

score 2 · Accepted Answer · answered Feb 05 '18 at 05:56

2

You can reference a data frame with the $ operator using a string literal, only a column. If you want to subset using a string, use the list syntax:

sub_df <- x_data[[some_string]]

answered Feb 05 '18 at 05:56

Tim Biegeleisen

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Thanks . This helps a lot. – Aargo Feb 05 '18 at 06:17

Subsetting columns by a string variable returns NULL in R

1 Answers1