delete the first n elements of each cell

Given cell a, how to delete the first n elements of each cell? I am now using for loop. However, when the loop is big (5021889 loops), this line can be very slow.

May I know if there is a faster version or vectorized version of this?

Thank you

    a=cell(2,1);
    a{1,1}=1:10;
    a{2,1}=1:10;
    b=[3,8];
    for i=1:2
        a{i,1}(1:b(i))=[];
    end

Answer 1

[Stephen]

I doubt that there is a much faster way, because what you are doing resizes the arrays themselves. cellfun will likely be slower.

[Guillaume]

Stephen is right, it's unlikely you can get faster (short of going the mex way and even then...)

However, when the loop is big (5021889 loops), this line can be very slow

No matter how you do it in matlab, truncating the first n elements of 5021889 array ultimately requires for each array:

• the reallocation of a new chunk memory. There's a lot of background check that needs to be done before memory is allocated so that's not a fast operation (relatively speaking),
• the copy of the required portion of original data in that new chunk of memory.

This has to be done 5021889 times, so it's going to be slow no matter what you do.

The only way to speed this up is to change your algorithm completely so that it is not required.

[Chaoyang Jiang]

Thank you for your answer.