MATLAB: Averaging specific elements from array

arraymean

Can I average specific elements on an array while ignoring others efficiently? For example, if have a text file like so:
Freq   Force   etc.
5      654     ....
5      754     ....
5      645     ....
10     1029    ....
10     1175    ....
10     1110    ....
15     1354    ....
15     1375    ....
15     1390    ....
Can I easily get the result:
Freq   Force  etc.
5      684    ....
10     1105   ....
15     1373   ....

Best Answer

You could use dlmread and accumarray:
>> M = dlmread('temp3.txt','',1,0)
M =
    5    654
    5    754
    5    645
   10   1029
   10   1175
   10   1110
   15   1354
   15   1375
   15   1390
>> [~,~,X] = unique(M(:,1));
>> A = accumarray(X,M(:,2),[],@mean)
A =
    684.33
   1104.67
   1373.00
Tested on the file attached to this answer.
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