[R] Scatterplot of two groups side-by-side?

[John Fox]

Dear Karin,

If I understand correctly what you want, the scatterplot function in the car
package isn't designed to produce it, but there are many ways to draw
side-by-side scatterplots. Here is one, using basic R graphics:

par(mfrow=c(1,2))
by(Data, Data$group, 
    function(x) {
        plot(Pulls ~ Resistance, data=x, main=paste("group =", group[1]))
        abline(lm(Pulls ~ Resistance, data=x))
        }
    )

This assumes that your data are in a data frame named Data, with variables
group, Pulls, and Resistance.

I hope this helps,
 John

------------------------------
John Fox, Professor
Department of Sociology
McMaster University
Hamilton, Ontario, Canada
web: socserv.mcmaster.ca/jfox


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
> Behalf Of nonunah at yahoo.de
> Sent: April-26-09 5:30 AM
> To: r-help at r-project.org
> Subject: [R] Scatterplot of two groups side-by-side?
> 
> Dear all
> 
> I'm realy new to R, so I hope you can help me, as I didn't find any
solution
> in the common books.
> 
> Since some days I'm trying to create the following plot: A scatterplott
> showning two different groups side-by-side with according regression
lines.
> Both datasets only have the same five factors, so the scatters will form a
> kind of column at each factor. When I use "scatterplot" (package "car"),
then
> I can plot two groups in the same graph by using the command "groups", but
> the scatters of both groups are then plotted on top of eachother using
> different symbols and they can hardly be distingushed. How can I plot them
> side by side, so that the groups do not overlap? And how can I give
different
> colours to the groups and the according regression line?(This is, what I
got
> so far: http://img7.imageshack.us/img7/227/almostgood.jpg)
> 
> I tried to use the commands used in "boxplot", to solve this problem. In
this
> commant, it's possible to plot different datasets side-by-side by defining
> the position of the bars (example: at = 1:5 - 0.4). A second boxplot-chart
> can then be added by adding the command "add=TRUE" to the line and
defining
> another position. Both commands don't function within the scatterplot-
> command.
> 
> By the way: It's realy necessary to plott the data as scatters and not as
> boxplots. With the command "plot", I can not plot the data by groups (I
tried
> it with the commands "subset" and "groups", but obviously, there is no way
to
> do so).
> 
> I'm greatful for every (simple) solution
> Thanks in advance
> 
> Karin Schneeberger
> MSc-student
> University of Berne
> Switzerland
> 
> 
> 
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> 
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