plotting cross sections of chemical data in groundwaters example of how to run the code
load data var=Sr cor=cor xx=[0:0.1:12] yy=[0:0.01:1.75] p_size=[400 60 1] levels=100 sing=1
interp_dat=plot_cs_chem(var,cor,xx,yy,p_size,levels,sing) - save the interpolated data in interp_dat
plot_cs_chem(var,cor,xx,yy,p_size,levels,sing) - just plot