 Sorting a matrix? - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: HP Prime (/forum-5.html) +--- Thread: Sorting a matrix? (/thread-4176.html) Sorting a matrix? - DrD - 06-18-2015 01:48 PM Looking for ideas: I need to row sort M1, an (n x 4) matrix, in decreasing order of column 4. Then on decreasing order of column 2, if sorted M1 contains more than one row with equal column 4 values. How can this be done? Thanks, -Dale- RE: Sorting a matrix? - DrD - 06-18-2015 03:26 PM This is bulky, but seems to work (better ideas?): Code: ``` EXPORT sm(N) BEGIN      M1:=CAS("randMat(N,3,ip(1..10))");     //  Generate random M1(N,3) cut list: M1[#pieces,length,width] of N patterns    for I from 1 to length(M1) do               M1(I,4):=M1(I,2)*M1(I,3);            //  Create column 4, M1[#pieces,length,width,area]      end;   for I from 1 to length(M1) do     for J from I+1 to length(M1) do       IF M1(I,4)if y!=x then return x>y else return x>y end; then sort(m,f) will sort a matrix m using f as a sort function. RE: Sorting a matrix? - DrD - 06-19-2015 10:28 AM Thank you for your very helpful suggestion! I like compact solutions like this, and I'll add it to my "how to" list for future reference. -Dale-