It would be an significant undertaking to annotate all the places
where the default behavior of strings-to-factors conversion might trip
up the unwary. You are not the first by any means to complain. You
might:
a) take the step that the Mayo Clinic has taken of setting the default
in options() to FALSE, or
b) make your own read.spss with your desired arguments, and then put
it in your .Rprofile.
--
David
On Jan 12, 2010, at 5:28 AM, RINNER Heinrich wrote:
Dear R-users,
I am using R version 2.10.1 and package foreign version 0.8-39 under
windows.
When reading .sav-Files (PASW Statistics 18.0.1) containing string
variables, these are automatically converted to factors when using
option "to.data.frame = TRUE" (see example below).
It's clear to me why this happens (the default behaviour of a call
to as.data.frame). But this is not always what one might want (or
even be aware of).
So maybe one of the following improvements could be made?
* Add a description of this behaviour in ?read.spss.
* Or (even better): Add an extra argument, like: read.spss("C:\\temp\
\test.sav", to.data.frame = TRUE, stringsAsFactors = FALSE).
Just a suggestion;
kind regards
Heinrich.
# EXAMPLE:
Suppose there is a simple file "test.sav", containing one variable
("x") of type STRING with 3 values (a,b,c).
library(foreign)
test <- read.spss("C:\\temp\\test.sav")
test
$x
[1] "a " "b " "c "
attr(,"label.table")
attr(,"label.table")$x
NULL
attr(,"codepage")
[1] 1252
is.factor(test$x)
[1] FALSE
is.character(test$x)
[1] TRUE
# Ok, that's just fine. But things change when using option
"to.data.frame = TRUE":
test <- read.spss("C:\\temp\\test.sav", to.data.frame = TRUE)
test
x
1 a
2 b
3 c
is.factor(test$x)
[1] TRUE
is.character(test$x)
[1] FALSE
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and provide commented, minimal, self-contained, reproducible code.
