[R] heatmap from xyz data

[Trevor Graham]

Hi,

I've got some data in a data frame arranged like this:
x	y	z	othervariables	....
0.1	0.2	1.7	0.01	....
0.2	0.2	1.3	0.23	....
0.2	0.3	1.1	0.43	....
etc

I'd like to plot a heatmap of this data, with x and y as the (x,y) co- 
ords and z defining the colour at each point.

I'm having difficulty finding the correct functions to use.  Can  
anyone make any recommendations?

It seems straightforward to make the plot using the image function if  
the data is in matrix form, but I'm not sure how to transform my xyz  
data into matrix form.

Many thanks in advance for your help.

Best wishes,
Trevor


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Trevor Graham
Centre for Mathematics and Physics in the Life Sciences and  
Experimental Biology (CoMPLEX)
Cancer Research UK

CoMPLEX, Wolfson House
University College London, Gower Street
London WC1E 6BT, UK
Tel: +44 (0)20 7679 5088
Internal: 25088
http://trevor.complex.ucl.ac.uk