R help - May 2003 - question about image command

Hello,

I have a question about image command. When you draw a image plot, and 
let's say we use gray scale. then how can I generate a little bar next to 
the plot which shows the grey levels and the values which corresponds to 
the grey level? ( it doesn't matter whether I am using grey level or not. 
It could be just any colors...)

The only way that I can do right now is overlaying contour plot on the 
image plot...

Thank you!

I wonder if filled.contour() does what you want:
   example(filled.contour)


Regards,

Andrew C. Ward

CAPE Centre
Department of Chemical Engineering
The University of Queensland
Brisbane Qld 4072 Australia
andreww at cheque.uq.edu.au

Quoting Mikyoung Jun <jun at galton.uchicago.edu>:
> Hello,
> 
> I have a question about image command. When you draw a image plot,
> and 
> let's say we use gray scale. then how can I generate a little bar
> next to 
> the plot which shows the grey levels and the values which
> corresponds to 
> the grey level? ( it doesn't matter whether I am using grey level
> or not. 
> It could be just any colors...)
> 
> The only way that I can do right now is overlaying contour plot on
> the 
> image plot...
> 
> Thank you!
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>

There are several options, the simplest is to use filled.contour() instead of 
image(). The output is slightly different, but that usually doesn't matter.

On Thursday 01 May 2003 09:26 pm, Mikyoung Jun wrote:
> Hello,
>
> I have a question about image command. When you draw a image plot, and
> let's say we use gray scale. then how can I generate a little bar next
to
> the plot which shows the grey levels and the values which corresponds to
> the grey level? ( it doesn't matter whether I am using grey level or
not.
> It could be just any colors...)
>
> The only way that I can do right now is overlaying contour plot on the
> image plot...
>
> Thank you!
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help

This is a regularly asked question and the solutions are varied.  The
default image() command does not place a legend on the plot.  There are 
three options that I know of:

1.  the image.plot()  function in the `fields' package.  This function has
similar syntax as image() but the resulting image can be difficult to
annotate sometime.

2.  the filled.contour() function in the `base' package produces nice
images but read the help page carefully if you want to add things
(text, points, etc) to the plot.

3.  the levelplot() function in the `lattice' package.  

The problem with 1 and 2 is that you cannot put more than one image on a
device because they use the layout() function.  levelplot() allows you to
put multiple images on the same device using a common legend.  Note that
levelplot() takes different arguments from image.plot() and
filled.contour().

-roger
_______________________________
UCLA Department of Statistics
http://www.stat.ucla.edu/~rpeng

On Thu, 1 May 2003, Mikyoung Jun wrote:
> Hello,
> 
> I have a question about image command. When you draw a image plot, and 
> let's say we use gray scale. then how can I generate a little bar next
to
> the plot which shows the grey levels and the values which corresponds to 
> the grey level? ( it doesn't matter whether I am using grey level or
not.
> It could be just any colors...)
> 
> The only way that I can do right now is overlaying contour plot on the 
> image plot...
> 
> Thank you!
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>