To find whether a column exists in data frame or not

Question

Assuming that the name of your data frame is dat and that your column name to check is "d", you can use the %in% operator:

if("d" %in% colnames(dat))
{
  cat("Yep, it's in there!\n");
}

You have a number of options, including using %in% and grepl:

dat <- data.frame(a=1:2, b=2:3, c=4:5)
dat
  a b c
1 1 2 4
2 2 3 5

To get the names of the columns:

names(dat)
[1] "a" "b" "c"

Use %in% to check for membership:

"d" %in% names(dat)
[1] FALSE

Or use `grepl` to check for a match:

grepl("d", names(dat))
[1] FALSE FALSE FALSE

You could use any:

> names(dat)
[1] "a" "b" "c"
> any(names(dat) == 'b')
[1] TRUE
> any(names(dat) == 'B')
[1] FALSE

You could also use if(!is.null(abcframe$d)) to test whether d exists in abcframe.

dat <- data.frame(a = 1:2, b = 2:3, c = 4:5)

if (!is.null(dat$d)) {
  print("d exists")
} else {
  print("d does not exist")
}
if (!is.null(dat$a)) {
  print("a exists")
} else {
  print("a does not exist")
}

A tidyverse approach might be more readable for some people, and therefore better to remember.

You would search for the variable by str_detect which returns a logical vector like grepl, and then collapse this by the base R function any which returns TRUE if there was at least one TRUE value.

dat %>% names %>% str_detect("d") %>% any()