You took the point.
Thanks a lot,
Nicola
David Winsemius ha scritto:
On Aug 15, 2010, at 4:32 AM, Nicola Spotorno wrote:
Dear all,
I'm quite new in R and I have a problem with the function which. When
I use it to select a subset of a dataframe it works well but
somewhere R takes trace of the past dataframe and this creates
problems with following operations.
For example:
sentences <- read.xls("frasi.tot.march.3.xls", header=TRUE)
head(sentences)
fam subjID Cond Code reg total first second
1 f 30 an fDan1 1 0.2812500 0.2812500 0.0000000
2 f 30 an fDan1 2 1.7851562 0.5390625 1.2460938
3 f 30 an fDan1 3 1.2304688 0.6679688 0.5625000
4 f 30 an fDan1 4 0.6289062 0.4375000 0.1914062
5 f 30 an fDan2 1 0.1367188 0.1367188 0.0000000
6 f 30 an fDan2 2 0.8632812 0.6679688 0.1953125
str(sentences)
'data.frame': 4799 obs. of 8 variables:
$ fam : Factor w/ 2 levels "f","uf": 1 1 1 1 1 1 1 1 1 1 ...
$ subjID: int 30 30 30 30 30 30 30 30 30 30 ...
$ Cond : Factor w/ 4 levels "an","fi","le",..: 1 1 1 1 1 1 1 1 1 1 ...
$ Code : Factor w/ 126 levels "fAan1","fAan2",..: 72 72 72 72 73 73
73 73 74 74 ...
$ reg : int 1 2 3 4 1 2 3 4 1 2 ...
$ total : num 0.281 1.785 1.23 0.629 0.137 ...
$ first : num 0.281 0.539 0.668 0.438 0.137 ...
$ second: num 0 1.246 0.562 0.191 0 ...
# If you look the variable "Cond" you see that it has 4 levels
sentences_trial <- sentences[which(sentences$Cond!= "an"),]
> str(sentences)
'data.frame': 4799 obs. of 8 variables:
$ fam : Factor w/ 2 levels "f","uf": 1 1 1 1 1 1 1 1 1 1 ...
$ subjID: int 30 30 30 30 30 30 30 30 30 30 ...
$ Cond : Factor w/ 4 levels "an","fi","le",..: 1 1 1 1 1 1 1 1 1 1 ...
$ Code : Factor w/ 126 levels "fAan1","fAan2",..: 72 72 72 72 73 73
73 73 74 74 ...
$ reg : int 1 2 3 4 1 2 3 4 1 2 ...
$ total : num 0.281 1.785 1.23 0.629 0.137 ...
$ first : num 0.281 0.539 0.668 0.438 0.137 ...
$ second: num 0 1.246 0.562 0.191 0 ...
# Now variable "Cond" still has 4 levels but with which I have
excluded one level!
You showed us two copies of str(sentences). How can we possibly know
what sentences_trial looks like?
#Whether I apply at this point interaction plot, the graph
considers 4 levels of which.
If you want to remove factor levels from a column just use factor() on
it again:
sentences_trial <- factor(sentences_trial$Cond)
Or to short-circuit that two-step process use subset with drop =TRUE:
sentences_trial <- subset( sentences, Cond!= "an" , drop=TRUE
attach(sentence_trial)
x11()
interaction.plot(Cond,fam,total)
# Where is the problem?
I think I identified it, but it was without a reproducible example so
it remains only an attractive theory.
David Winsemius, MD
West Hartford, CT
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