Re: any better to apply a function to second column?

*To*: mathgroup at christensen.cybernetics.net*Subject*: [mg518] Re: [mg507] any better to apply a function to second column?*From*: Lou Talman <me at talmanl.mscd.edu>*Date*: Tue, 7 Mar 95 08:35:57 -0700

On Tue 07 Mar 1995, Richard Chen wrote: > Suppose I have list of numbers in pairs: > a = {{x1,y1},{x2,y2},...,{xn,yn}} > I would like to apply to the sequence {y1,y2,...,yn} the function > f so that a new sequence > > b = {{x1,f[y1]},{x2,f[y2]},...,{xn,f[yn]}} > > is generated. > > My current solution is > > b = Transpose[{First /@ a,f[Last /@ a]}] > > However, I suspect there should be a much more simpler way than this. > > Does any body know a more straight forward way to do this? Yes. Map[MapAt[f, #, 2]&, a] will accomplish what you want. > Also, what if I have a matrix of 3 or more columns and I would apply > f to only the second column, say. What is a better way in this case? The same instruction works in this case as well. --Lou Talman Metropolitan State College of Denver