Hi,
Here are some links, from previous posts, on ternary plots.
http://www.prodomosua.it/zips/triangolare.xls
http://www.sfu.ca/~marshall/ternplot.htm
http://www.uni-wuerzburg.de/mineralogie/links/drawing/ternary.html
http://www.geologynet.com/programs/ternplot.xls
http://www.lboro.ac.uk/research/phys-geog/tri-plot/
http://www.agri.upm.edu.my/~chris/tal/talxl.html
ftp://www-sst.unil.ch/ftp/jfurrer/Trix_fr.zip
http://www-sst.unil.ch/perso_pages/jfurrer/Applications/Trixcel/Trixc...
Cheers
Andy
> I'm interested in drawing 2-D graphs of equations with 3 variables - a
> triangular ternary graph would be good. Are there any add-ins for Excel that
> would allow me to do this?

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Andy Pope, Microsoft MVP - Excel
http://www.andypope.info