From help-octave-request at bevo dot che dot wisc dot edu Thu Dec 20 11:23:47 2001
Subject: Re: scatter-plotting by color
From: Paul Kienzle <pkienzle at jazz dot ncnr dot nist dot gov>
To: John Day <jday at csihq dot com>
Cc: help-octave at bevo dot che dot wisc dot edu
Date: Thu, 20 Dec 2001 12:22:55 -0500

AFAIK, gnuplot doesn't have fine grained color control, so you might have
trouble with this.  I don't know about plplot.

Here's a possibility:

	# generate some data
	x = rand(30,1);
	y = rand(size(x));
	C = rand(size(x));
	# define a colormap that uses different colors for all its points
	map=hsv(64);
	map(1,:)=[1,1,1];
	colormap(map);
	# convert your x,y coordinates to image coordinates
	xi = 1+round((x-min(x))/(max(x)-min(x))*399);
	yi = 1+round((y-min(y))/(max(y)-min(y))*399);
	# use implicit sparse->full conversion to build an image array
	# use conv2 to spread spread the points out a bit (ones(5) makes
	# them into a 5x5 square, but you could easily define another shape
	matrix = conv2(sparse(xi,yi,C,400,400),ones(5),'same');
        # if we had a proper image viewer, we could define the x and y
	# axes as well:
	xstep = linspace(min(x),max(x),400);
	ystep = linspace(min(y),max(y),400);
	imagesc(xstep,ystep,matrix);
	# or if you have epsTk:
	eopen("scatter.ps");
	eglobpar;
	eaxes([min(x),(max(x)-min(x))/10,max(x)],[min(y),(max(y)-min(y))/10,max(y)]);
	eimagesc(matrix,map,'e');
	eclose
	eview

Paul Kienzle
pkienzle at users dot sf dot net

On Wed, Dec 19, 2001 at 07:24:59PM -0500, John Day wrote:
> I have a file of 3-tuples (X,Y,C), where C is an integer 1-16, which I want 
> to scatter-plot, X by Y with C determining the color of the plotted dots.
> 
> Does anyone know or have a ready-made function to do this? I don't care 
> what the colors are as long as they are unique for each value of C. 
> Different-shaped dots will do if we run out of colors.
> 
> Thanks,
> John Day
> 
> 
> 
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