Question

I’ve created 3 vectors:

v1 = c(1,2,3)
v2 = c(11,22,33)
v3 = c(111,222,333)

Then I’ve made a frame from them:

> df = data.frame(vec1 = v1, vec2 = v2, vec3 = v3)                                                                                                                                
> df
  vec1 vec2 vec3
1    1   11  111
2    2   22  222
3    3   33  333

It seems like column names is not automatic now, but vec1, vec2, vec3.

After this I want to get a frame row where vec2 is equal to 11:

> df[vec2 == 11,]
Error in `[.data.frame`(df, vec2 == 11, ) : object 'vec2' not found

But the following code works:

> df[v2 == 11,]
  vec1 vec2 vec3
1    1   11  111

I think this is wrong. I don’t understand why R uses old vector names, instead of tags vec1, vec2, vec3.

Is it a bug of my version of R?

R version 2.15.2 (2012-10-26)
Platform: x86_64-apple-darwin12.2.0/x86_64 (64-bit)

Answer 1

Either use:

df[df$vec2 == 11, ]

or

df[with(df, vec2 == 11), ]

The second one worked because v2 == 11 evaluates to TRUE, FALSE, FALSE and so, the first row was being printed. However, vec2 is not a variable that is set. It is a column of a data.frame. So, you’ll have to identify it as such with df$vec2 (or use with)