MATLAB: Data manipulation question, need some help!!

data manipulationmatrix array

Guys, I really need some help here. I got stuck for a long time.
1. How am I supposed to create a matrix that has two columns, the format of the first one is string, and the second is numerical?
Say a = ['1';'2';'3'], b = [4,5,6], I need to create a matrix like c =
      1      4
      2      5
      3      6
I tried to use c = {a,b}, but the answer is c = [3×1 char] [3×1 double]
2. A =
          '15'      3854
          '10'      6331
          '10'      4324
          '20'      3874
          '25'      4321
          '15'      6835
          '10'      3321
          '15'      3821
          '20'      9324
I need to sum the 2nd column according to the 1st column and create a new matrix. E.g, for '10', I should sum up (6331,4324,3321) , the final result should be
B =
                  '10'        13976
                  '15'        10689
                  '20'        13198
                  '25'         4321
Any opinion is welcomed!

Best Answer

A ={...
'15'      3854
'10'      6331
'10'      4324
'20'      3874
'25'      4321
'15'      6835
'10'      3321
'15'      3821
'20'      9324}
[a b b] =  unique(A(:,1));
out = [a num2cell(accumarray(b,cat(1,A{:,2})))];
OR
out2 = [str2double(a) accumarray(b,cat(1,A{:,2}))];
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