Sander,
has anybody made an attempt to create the soil texture triangle >graph
in R? See ternaryplot() in package vcd. Its options are quite limited, but it may help. I think you'll need to write your own function to do a ternary plot like the one you point to, perhaps using functions in the grid package as your building blocks. Scott Waichler, Senior Research Scientist Pacific Northwest National Laboratory scott.waichler at pnl.gov