
Re: Average the same elements of the list
Posted:
May 23, 2013 3:55 AM


You didn't specify what to return in case the first elements of the sublists are NOT all the same; let's return the entire original list in this case. Then perhaps something like the following will do.
op[lis_] := If[And @@ MapThread[Equal, First /@ lis], {First@First@lis, Mean[Last /@ lis]}, lis]
op[{ {{2, 5, 1}, d1}, {{2, 5, 1}, d2}}] (* { {2, 5, 1}, (d1 + d2)/2 } *)
op[{{{2, 5, 1}, d1}, {{2, 9, 1}, d2}}] (* {{{2, 5, 1}, d1}, {{2, 9, 1}, d2}} *)
Undoubtedly the code can be shortened.
On May 22, 2013, at 2:18 AM, BBabic <bipsich101@gmail.com> wrote:
> Hello, > I have list which is something like > data={ > {{a1,b1,c1},d1},{{a2,b2,c2},d2}} > I would like to get new list which gets average of the second elements if the first elements in the sublists are all the same. > Namely if a1=a2,b1=b2,c1=c2 > new list would look like > datanew={{a1,b1,c1},Mean[{d1,d2}] > Is there an elegant way to do this ? > Thanks!
 Murray Eisenberg murray@math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 5491020 (H) University of Massachusetts 413 5452838 (W) 710 North Pleasant Street fax 413 5451801 Amherst, MA 010039305

