How to sum the second position data in an array (50000x2) with the same value in the first position
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    Borja Zamarreño
 on 3 Jun 2020
  
    
    
    
    
    Edited: Borja Zamarreño
 on 10 Jun 2020
            Hello everyone im having some issues trying to solve this. I have an array with this form
A=
   2.79314   0.007
   2.79314   0.083
   2.79314   0.051
   2.91205   0.06
   2.91205   0.06
   2.97143   0.08
   2.97143   0.06
   2.97143   0.07
   2.97143   0.08
What i want is that whenever the data of the first column is the same, sum the data in the second column.This is what I want to obtain:
B= 
   2.79314   (0.007+0.083+0.051)
   2.91205   (0.06+0.06+0.08)
   2.97143   (0.08+0.06+0.07+0.08)
Thnak you very much in advance.
Regards.
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Accepted Answer
  Stephen23
      
      
 on 3 Jun 2020
        
      Edited: Stephen23
      
      
 on 3 Jun 2020
  
      Method one: accumarray:
>> [U,~,G] = uniquetol(A(:,1));
>> S = accumarray(G(:),A(:,2));
>> M = [U,S]
M =
   2.79314   0.14100
   2.91205   0.12000
   2.97143   0.29000
Mehod two: splitapply:
>> S = splitapply(@sum,A(:,2),G);
>> M = [U,S]
M =
    2.7931    0.1410
    2.9120    0.1200
    2.9714    0.2900
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