Thanks to Eurogenes project member DESEUK1. A zip file with the R script, instructions and a couple of data sheets is available here.
So let's model Poles as a bunch of ancient genomes from Central and Eastern Europe using output from my K8 analysis.
Copy & Paste: source('4mix.r')
Copy & Paste: getMix('K8avg.csv', 'target.txt', 'HungaryGamba_EN', 'HungaryGamba_HG', 'Karelia_HG', 'Corded_Ware_LN')
After a few seconds you should see the results...
Target = 19% HungaryGamba_EN + 14% HungaryGamba_HG + 2% Karelia_HG + 65% Corded_Ware_LN @ D = 0.0062
Obviously the script can use ancestry proportions and/or population averages from any test, provided they're formatted properly. The accuracy of the modeling will depend on the quality of the input.
Update 19/05/2015: A new version of the 4mix script that can run multiple targets is available here, courtesy of Open Genomes.