Pedro Fernández Martínez wrote: > I get the error: > > > ! Undefined control sequence. > <recently read> \c at lor@to at ps > > l.15 \psline[linewidth=1pt,linecolor=gray]{<->} > > (0.5,0)(0,1)(1,1.5)(1.5,1)(... > > ? > > Anything I did wrong? or anything I didn't? looks like you run pdflatex? Instead of latex. Herbert