R help - Apr 2007 - Tweaking my plot of matrix as image

Greetings list,

I have a rectangular 20 x 20 matrix with values in the range of [0 ,  
1]. I'd like to plot it as an image. To that end, I have used the  
image() function that seems to do what I want. Now, I just want to  
tweak it to look perfect. So here is my question:

At the moment, the values of the axis range from [0, 1]. I want it to  
show the row and column of the matrix. How do I do that?

  Thanks in advance.

Wee-Jin

Hi

Did you by chance look at the help page of image? If you did, you could 
read


x,y
locations of grid lines at which the values in z are measured. These must 
be finite, non-missing and in (strictly) ascending order. By default, 
equally spaced values from 0 to 1 are used. If x is a list, its components 
x$x and x$y are used for x and y, respectively. If the list has component 
z this is used for z.
z
a matrix containing the values to be plotted (NAs are allowed). Note that 
x can be used instead of z for convenience.

and therefore

image(1:20, 1:20, your.matrix)

shall do what you probably want. And if you have different matrix size 
then

1:dim(your.matrix)[1]

can give you suitable sequence.

Regards

Petr Pikal
petr.pikal at precheza.cz

r-help-bounces at stat.math.ethz.ch napsal dne 12.04.2007 10:55:21:
> Greetings list,
> 
> I have a rectangular 20 x 20 matrix with values in the range of [0 , 
> 1]. I'd like to plot it as an image. To that end, I have used the 
> image() function that seems to do what I want. Now, I just want to 
> tweak it to look perfect. So here is my question:
> 
> At the moment, the values of the axis range from [0, 1]. I want it to 
> show the row and column of the matrix. How do I do that?
> 
>   Thanks in advance.
> 
> Wee-Jin
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Wee-Jin Goh wrote:
> Greetings list,
> 
> I have a rectangular 20 x 20 matrix with values in the range of [0 ,  
> 1]. I'd like to plot it as an image. To that end, I have used the  
> image() function that seems to do what I want. Now, I just want to  
> tweak it to look perfect. So here is my question:
> 
> At the moment, the values of the axis range from [0, 1]. I want it to  
> show the row and column of the matrix. How do I do that?
> 
Perhaps color2D.matplot will suit you. It automatically shows the row 
and column indices on the plot in the same order as conventional matrix 
displays.

Jim