Binning data from two columns using one column as category for second column

Hi all,

So I am trying to do this via loops but i am not getting anywhere and i am sure that there is a quicker way to solve this problem. I have two columns of data, Radius and Volume, and I wanted to bin the Volume according to the values of the Radius. So for example, if R is the first column of values and V is the second column

    A = [ 1 8
          2 7
          3 9
          4 3
          5 4
          6 6
          7 5
          8 6
          9 6
          10 6
          11 3
          12 2
          13 1
          14 1
          15 3
          16 4
 ]

will be binned as

B = [   5 31
        10 29
        15 10
        ]

So the bin labels are the values of the Radius, and the second column contains the sum of the Volumes in that Radius range.

Many thanks

[Star Strider]

Please explain in some detail how you get ‘B’ out of ‘A’.

[Jos (10584)]

which Radius range?

[Sohrab Daemi]

So the first column in matrix B is the radius binned with a bin size of 5 (so 5, 10, 15, 20, 25, 30) and the second column is the sum of the values of the volume within each radius range ( so all the volumes for radius was under 5 are summed etc)

Answer 1

[Jos (10584)]

[~,i] = histc(X,edges)
Result = accumarray(Y,i,[max(i) 1],@sum)

[Sohrab Daemi]

Thanks, I am trying to use this but am having an error message. I assume X= A(:,1) and Y = A(:,2) and edges = bin size?

Thanks again

[Jos (10584)]

Almost correct! See the help of HISTC about the meaning of the second input argument ( edges).