I have datasets containing a number of pairs each pair of variable length with longest set governing the column length. They are beach cross sections and I am trying examine the change specific contours. I can do this by individually working each pair but because of the number of sets would like to automate. I have compiled the following h=read.csv("testxsec.csv",header=T) for(i in seq(1,(ncol(h)-1),by=2)){ s=seq(from=7,to=9,by=0.25) d=data.frame(h[,i:(i+1)]) f=approx(x=d[,1],y=d[,2], xout=s, method="linear", yleft=0.125, yright=0.125, rule = 2, f = 0, ties = mean,na.omit) } I cannot get the calculation to give me a set of approximations. I am expecting that for each of the values of "s" I will have an approximation for each x/y pair in the set. Any help appreciated greatly [[alternative HTML version deleted]]