R help - Aug 2007 - image plot with multiple x values

Hi,

New to R, I don't find a way to plot the following data with image():

x is a N * M matrix
y is a vector of length M
z is a N*M matrix

I wish to plot z as a greyscale image, but my x axis is different for  
every row of the z data.

Here is a minimal example,
> theta<-c(3:6) # N
> y<-c(1:5) # M
>
> x<-theta%*%t(y)# N * M
> z<-sin(x) # N * M
>
> image(z)
This doesn't give what I want, as the x axis needs to be shifted as  
we go from line to the following. (probably clearer if you plot  
matplot(x,z): the curves are shifted)

The way I see it, I need either to construct a bigger matrix with all  
possible values of x giving the new dimension and arbitrary values  
for the missing points, or find a plotting function that would plot  
lines by lines. The ordering of the x and z values is giving me a  
headache on the first idea, and I can't find any option / alternative  
to image.

Thanks in advance!

baptiste

On Fri, Aug 17, 2007 at 07:51:59PM +0100, baptiste Augui?
wrote:
> Hi,
> 
> New to R, I don't find a way to plot the following data with image():
...
> This doesn't give what I want, as the x axis needs to be shifted as  
> we go from line to the following. (probably clearer if you plot  
> matplot(x,z): the curves are shifted)
Perhaps you could plot "points" each of which would be a colored
square, at the locations given by x,y ??

along the lines of 

plot(y~x,col=z,pch=15,cex=5) 

/* pch = 15 plots a filled square, cex=5 makes the square bigger, you
could try different values of cex*/


-- 
Daniel Lakeland
dlakelan at street-artists.org
http://www.street-artists.org/~dlakelan

If you are willing to go to the bother of representing your data
as a sparse matrix, the package SparseM has a version of image()
that will do what you would like to do, I believe.


url:    www.econ.uiuc.edu/~roger            Roger Koenker
email    rkoenker at uiuc.edu            Department of Economics
vox:     217-333-4558                University of Illinois
fax:       217-244-6678                Champaign, IL 61820


On Aug 17, 2007, at 1:51 PM, baptiste Augui? wrote:
> Hi,
>
> New to R, I don't find a way to plot the following data with image():
>
> x is a N * M matrix
> y is a vector of length M
> z is a N*M matrix
>
> I wish to plot z as a greyscale image, but my x axis is different for
> every row of the z data.
>
> Here is a minimal example,
>
>> theta<-c(3:6) # N
>> y<-c(1:5) # M
>>
>> x<-theta%*%t(y)# N * M
>> z<-sin(x) # N * M
>>
>> image(z)
>
> This doesn't give what I want, as the x axis needs to be shifted as
> we go from line to the following. (probably clearer if you plot
> matplot(x,z): the curves are shifted)
>
> The way I see it, I need either to construct a bigger matrix with all
> possible values of x giving the new dimension and arbitrary values
> for the missing points, or find a plotting function that would plot
> lines by lines. The ordering of the x and z values is giving me a
> headache on the first idea, and I can't find any option / alternative
> to image.
>
> Thanks in advance!
>
> baptiste
>
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