R help - Mar 2011 - various plotting options

Dear R-Project helpdesk member,

I am currently working on some basic correspondence analysis using the R
packages 'ca'. As I compute the CA by example <- ca(data), and
plotting example via plot(example), I am trying to figure out, how to get a
certain desired plot, so, however, my question could be of more general nature.

This probably might not be new to you, but the plotting the result of ca will
return a plot, with red points (triangles if I remember correctly) labeled with
the column names of the original table read in, and blue dots for the row names.
What I essentially need to solve is, to make a plot, which differs in the
visualization of the rows. The labels of the rows should not be displayed at
all, plus, certain rows must have a different color of other rows. Of course, I
looked up several manuals and threads already, but unfortunatly I was not able
to get very far beyond "plot(example, labels=0)".

So let us say, I have a table, which looks like this
a b c d
a 1 2 3
b 4 5 6
c 7 8 9
d 0 1 2

with a b c d being the header, and the row.names=1, what I practically need is a
plot, that displays the column names attached as labels to the corresponding
dots/triangles (which is the default case), and the dots referring to the rows
without(!) any labels, PLUS  the points corresponding to the first two rows (a=1
2 3, b = 4 5 6) in a different color (really does not matter which) than the
points corresponding to the last two ones (c = 7 8 9, d = 0 1 2).

I deeply hope, that you are able to help me; if I can help you considering the
formulation of my question, please feel free, to contact me.

With kind regards, I appreciate your work,
-Patrick Grossmann

On 3/23/2011 10:27 AM, Grossmann Patrick wrote:
>      Dear R-Project helpdesk member,
>
> I am currently working on some basic correspondence analysis using the R
packages 'ca'. As I compute the CA by example<- ca(data), and
plotting example via plot(example), I am trying to figure out, how to get a
certain desired plot, so, however, my question could be of more general nature.
>
> This probably might not be new to you, but the plotting the result of ca
will return a plot, with red points (triangles if I remember correctly) labeled
with the column names of the original table read in, and blue dots for the row
names. What I essentially need to solve is, to make a plot, which differs in the
visualization of the rows. The labels of the rows should not be displayed at
all, plus, certain rows must have a different color of other rows. Of course, I
looked up several manuals and threads already, but unfortunatly I was not able
to get very far beyond "plot(example, labels=0)".
>
> So let us say, I have a table, which looks like this
> a b c d
> a 1 2 3
> b 4 5 6
> c 7 8 9
> d 0 1 2
>
> with a b c d being the header, and the row.names=1, what I practically need
is a plot, that displays the column names attached as labels to the
corresponding dots/triangles (which is the default case), and the dots referring
to the rows without(!) any labels, PLUS  the points corresponding to the first
two rows (a=1 2 3, b = 4 5 6) in a different color (really does not matter
which) than the points corresponding to the last two ones (c = 7 8 9, d = 0 1
2).
>
> I deeply hope, that you are able to help me; if I can help you considering
the formulation of my question, please feel free, to contact me.
[First: please use a more specific and informative subject line in posts 
to R-help]

The plot function in the ca package is a bit crippled, since you have no 
control over the colors/plot symbols for subsets of the row/col points,
so I'm afraid you can't do what you want with the current CRAN version.

I modified ca::plot.ca.r to return the matrix of coordinates actually 
plotted, allowing me to use points() and lines() after the call.
I can send that to you if you like.

HTH

-- 
Michael Friendly     Email: friendly AT yorku DOT ca
Professor, Psychology Dept.
York University      Voice: 416 736-5115 x66249 Fax: 416 736-5814
4700 Keele Street    Web:   http://www.datavis.ca
Toronto, ONT  M3J 1P3 CANADA