How to find the column index in an R data frame that matches a condition?

To find the column index that matches a condition, we can use apply function. This condition could be values in columns greater than something, less than something, equal to something, or any other condition for numerical variables. For example, if we want to check which columns of data df contains value in rows greater than 5 then we can use the command apply(df,1, function(x) which(x>5)).

Consider the below data frame −

Example

 Live Demo

x1<-rnorm(20,2,0.05) x2<-rnorm(20,2,0.65) df1<-data.frame(x1,x2) df1

Output

      x1      x2 1  2.083832  3.238437 2  1.999989  2.409343 3  1.908010  2.088710 4  1.914835  2.421812 5  2.080797  1.705331 6  1.977896  1.337907 7  1.987243  2.687881 8  2.002822  2.850734 9  1.932333  2.470400 10 1.955817  1.652495 11 2.085809  1.490701 12 1.986614  1.733392 13 1.975024  1.742006 14 1.983986  2.441801 15 1.991714  2.450637 16 1.947738  1.105244 17 2.052789  2.020752 18 1.989781  1.438219 19 2.023067  1.615221 20 2.086341  3.046352

Checking which columns of df1 have value greater than 1.5 for each row −

apply(df1,1, function(x) which(x>1.5))

[[1]] x1 x2  1 2 [[2]] x1 x2  1 2 [[3]] x1 x2  1 2 [[4]] x1 x2  1 2 [[5]] x1 x2  1 2 [[6]] x1 1 [[7]] x1 x2  1 2 [[8]] x1 x2  1 2 [[9]] x1 x2  1 2 [[10]] x1 x2 1 2 [[11]] x1 1 [[12]] x1 x2  1 2 [[13]] x1 x2  1 2 [[14]] x1 x2 1 2 [[15]] x1 x2  1 2 [[16]] x1 1 [[17]] x1 x2  1 2 [[18]] x1 1 [[19]]  x1 x2 1 2 [[20]] x1 x2  1 2