Combining duplicate entries in a data array

Hello,

I have two vectors x and y with corresponding data points. x is in sorted order, but may have double entries, e.g.

x = [0.1, 5, 5, 5, 14.5, 16, 16, 21];
y = [70, 8, 2, 3.5, 6, 5, 2.5, 3.3];

What I would like to do is find the double entries of x and combine the corresponding y values (by summing them up), so that

x_new = [0.1, 5, 14.5, 16, 21];
y_new = [70, 8+2+3.5, 6, 5+2.5, 3.3] = [70, 13.5, 7.5, 3.3];

However I struggle to manage this sufficiently. I have tried to use the function

[x_new, ia, ic] = unique(x);

but I don't know how to efficiently use these values further. Any ideas? :)

Thanks for your help!

Answer 1

[Stephen23]

Use accumarray:

>> x = [0.1, 5, 5, 5, 14.5, 16, 16, 21];
>> y = [70, 8, 2, 3.5, 6, 5, 2.5, 3.3];
>> [xnew,~,idx] = unique(x);
>> ynew = accumarray(idx(:),y(:))
ynew =
   70.0000
   13.5000
    6.0000
    7.5000
    3.3000

[Addo]

Works perfectly! Thanks for your help!

[Batuhan Arik]

Hello, did the exact same thing, it seems to be working. I get x_new and y_new as they are supposed to come out. However, when I try

bar(x_new,y_new); 

the plot comes out empty.