如何在Matlab中将向量与异步时间戳对齐？

Question

I would like to align and count vectors with different time stamps to count the corresponding bins.

Let's assume I have 3 matrix from [N,edges] = histcounts in the following structure. The first row represents the edges, so the bins. The second row represents the values. I would like to sum all values with the same bin.

A = [0 1 2 3 4 5;
     5 5 6 7 8 5]

B = [1 2 3 4 5 6;
     2 5 7 8 5 4]

C = [2 3 4 5 6 7 8;
     1 2 6 7 4 3 2]

Now I want to sum all the same bins. My final result should be:

result = [0 1 2 3 4 5 6 7 8;
          5 7 12 16 ...]

I could loop over all numbers, but I would like to have it fast.

Answer 1

You can use accumarray :

H = [A B C].';   %//' Concatenate the histograms and make them column vectors

V = [unique(H(:,1)) accumarray(H(:,1)+1, H(:,2))].';   %//' Find unique values and accumulate

V =

    0    1    2    3    4    5    6    7    8
    5    7   12   16   22   17    8    3    2

Note: The H(:,1)+1 is to force the bin values to be positive, otherwise MATLAB will complain. We still use the actual bins in the output V . To avoid this, as @Daniel says in the comments, use the third output of unique (See: https://stackoverflow.com/a/27783568/2732801 ):

H = [A B C].';  %//' stupid syntax highlighting :/
[U, ~, IU] = unique(H(:,1));
V = [U accumarray(IU, H(:,2))].';   

Answer 2

If you're only doing it with 3 variables as you've shown then there likely aren't going to be any performance hits with looping it.

But if you are really averse to the looping idea, then you can do it using arrayfun .

rng = 0:8;
output = arrayfun(@(x)sum([A(2,A(1,:) == x), B(2,B(1,:) == x), C(2,C(1,:) == x)]), rng);

output = cat(1, rng, output);

    output =

        0     1     2     3     4     5     6     7     8
        5     7    12    16    22    17     8     3     2

This can be beneficial for particularly large A , B , and C variables as there is no copying of data.