Hi Nicola,
Although you have subsetted the data.frame, the factor variable will
still include the empty level.
For example, the following...
foo <- data.frame(f = factor(c("a", "b", "c", "b", "a")), val = 1:5)
foo2 <- foo[ foo$f != "a", ]
foo2
str(foo2)
Produces this output...
f val
2 b 2
3 c 3
4 b 4
'data.frame': 3 obs. of 2 variables:
$ f : Factor w/ 3 levels "a","b","c": 2 3 2
$ val: int 2 3 4
You can drop the unused factor level "a" like this...
foo2$f <- foo2$f[, drop=TRUE]
str(foo2)
'data.frame': 3 obs. of 2 variables:
$ f : Factor w/ 2 levels "b","c": 1 2 1
$ val: int 2 3 4
Michael
On 15 August 2010 22:03, Nicola Spotorno <[email protected]> wrote:
> Hello,
> thanks for your replies, but the logic operator is '!='. If I call
> sentence_trial the dataframe shows no 'an' datapoints as I want but I
> still have problems with 'str' and 'interaction_plot'.
>
> Nicola
>
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