Data manipulation question, need some help!!
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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 = [3x1 char] [3x1 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!
2 Commenti
Tom
il 18 Giu 2012
If the first column is always numerical, would it be easier to convert the strings to numbers, then convert back to strings when needed?
Risposta accettata
Andrei Bobrov
il 18 Giu 2012
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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