James, Sara, Thierry and all others:
R2013b doesn't have the start button anymore. To install, get your path to ezyfit (setpath) and save it in the Environment tab. Then there is a hard coded problem in efmenu.m at line 212. The semi-colon should be a colon:
212 sufolder = strrep(userpath,':','');
I have a question: is there a way to force variables being smaller than a certain value or within an interval?
F.i. something like f=ezfit(x,y,'a/(1+exp(-b*(x-c)))+d;a=8&a>0;b<1&b>0;c=70;d=0'); (this of course does not work)