Hi John,
The problem seems to be with the order in which the 'levels' of
the conditioning variable appear. Here's a reproducible example:
Prestige$tp<- with(Prestige, ifelse(type == "prof", 0, 1))
scatterplot(prestige ~ income | tp, data=Prestige)
Note that I've just switched the 0/1 from your example.
A quick look at scatterplot.formula suggests that wrapping
the 'X[, 3]' in this line
scatterplot(X[, 2], X[, 1], groups = X[, 3], xlab = xlab,
inside an as.factor() would solve the problem.
-Peter
On 2010-04-25 8:40, John Fox wrote:
Dear Peter and Anthony,
Thanks, Peter, for answering the question, but scatterplot() should work
even if z is not a factor, and does for me in the following example:
library(car)
Prestige$tp<- with(Prestige, ifelse(type == "prof", 1, 0))
scatterplot(prestige ~ income | tp, data=Prestige)
So, Anthony, the usual advice about providing a reproducible example seems
applicable here.
Regards,
John
--------------------------------
John Fox
Senator William McMaster
Professor of Social Statistics
Department of Sociology
McMaster University
Hamilton, Ontario, Canada
web: socserv.mcmaster.ca/jfox
-----Original Message-----
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org]
On
Behalf Of Peter Ehlers
Sent: April-24-10 11:57 PM
To: Anthony Lopez
Cc: R-help@r-project.org
Subject: Re: [R] categorical variable in scatterplot (car)
On 2010-04-24 21:30, Anthony Lopez wrote:
Hello R folks,
I am encountering a problem with the following scatterplot function from
the
car package:
scatterplot(y~x|z)
where y and x are continuous (interval) random variables and z is a
categorical variable. When z is a categorical variable coded 1 or 2, I
(appropriately) get a scatterplot of y by x, coded by z. Similarly,
when z
is a categorical variable coded 1, 2, or 3, there is again, no problem.
However, when z is a categorical variable coded 0 or 1, the
scatterplot
scatterplot(y~x|z)
is exactly identical to the one generated by
scatterplot(y~x)
It is not possible that this is due to the fact that there is no
difference
between the categories. It is as if R doesn't "see" that I want it
coded
by
z. But this only happens when one of the categories of z is coded "0"
(i.e.
zero). Any ideas why this is so, or how I can fix this without recoding
my
variable?
Make z a factor (which it really should be anyway).
-Peter Ehlers
Thank you!
Anthony
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PLEASE do read the posting guide http://www.R-project.org/posting-
guide.html
and provide commented, minimal, self-contained, reproducible code.
--
Peter Ehlers
University of Calgary
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
--
Peter Ehlers
University of Calgary
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
