Question

Lets say,we’ve the following two vectors:

data =   [1 2 2 2 3 3 3 3 3 3 4 4 4 4 4 ];
x_axis = [1 1 1 2 2 2 3 3 3 3 3 4 4 5 5 ];

What i now want to have is to count all data values which are for example one in the x_axis ,then these values which are two etc. So the result should look like as following (which i then can represent as a histogram):

  result=[5 8 16 8 8];
  x_axis=[1 2  3 4 5];

Answer 1

This is the perfect application example for accumarray:

data =   [1 2 2 2 3 3 3 3 3 3 4 4 4 4 4 ];
x_axis = [1 1 1 2 2 2 3 3 3 3 3 4 4 5 5 ];

result = accumarray(x_axis(:),data(:),[],@sum)
result =
 5
 8
16
 8
 8