Extraction of a sub matrix from a mother matrix

Hi, I have a matrix A = [0 0 1 1 0 0 0 1 1 1 1 1 0 0 0 0 1 1 1 0 0 1]. I want to sum the 1's of its duration so that the result comes as B = [0 0 2 0 0 0 5 0 0 0 0 3 0 0 1]. I need a help in this regard.

Answer 1

[Jan]

With FEX: RunLength:

A = [0 0 1 1 0 0 0 1 1 1 1 1 0 0 0 0 1 1 1 0 0 1];
[B, N]   = RunLength(A);
match    = (B == 1);
B(match) = N(match);
N(match) = 1;
Result   = RunLength(B, N);

[EDITED] And after a lot of time and struggling a working loop:

R  = zeros(1, numel(A) + 1);
iR = 1;
for k = 1:numel(A)
    if A(k) == 0
        iR = iR + 1 + (R(iR) ~= 0);
    else
        R(iR) = R(iR) + 1;
    end
end
R = R(1:iR - (R(iR) == 0))

[Amitrajit Mukherjee]

RunLength command is not responding

[Birdman]

How about my answer? Doesn't it look more simpler?

[Amitrajit Mukherjee]

Hey nice..Yes, this is more easier and working well..Thank you.. :) :)

[Jan]

@Amitrajit Mukherjee: What does "RunLength command is not responding" mean? You have to download it at first from the FileExchange. While RunLength is a fast C-Mex function and has to be compiled at first, RunLength_M is an M-function and can be used directly.

[Amitrajit Mukherjee]

See, now I actually needed it without downloading any extension..So I would like to prefer the second code which you have suggested..I will also try other codes later..I need a versatile Code which can be used in such computers with no internet..So no option will be there to download any MATLAB function..But other options are also appreciable..Thanks..

[Jan]

@Amitrajit Mukherjee: You can download the files on the computer you use to post in the forum and include the source codes in your program. Copying the code from the forum is not a real difference to copying code from the FileExchange.

Answer 2

[Birdman]

Firstly, download the file from the following link and use rcumsum function within it.

https://www.mathworks.com/matlabcentral/fileexchange/28685-rcumsumc

Then, apply the following code:

B=rcumsum(A);
idx=setdiff(find(diff(B)==1),find(diff(B)<0)-1)+1;idx(end)=[];
B(idx)=[]

[Stephen23]

"How about my answer? Doesn't it look more simpler?"

[Birdman]

But mine is also simpler, right? :) At least no for loops, which is an improvement for me.

[Stephen23]

"But mine is also simpler, right?"

Your answer calls both diff and find twice, setdiff once, requires four lines, and resizes two arrays.

My answer calls diff once, requires two lines, and is simpler.

[Amitrajit Mukherjee]

Sorry rcumsum is not working in this version.. :( :(

[Stephen23]

@Amitrajit Mukherjee: did you download it, as Birdman clearly told you to do? The function contains only standard MATLAB commands, so there is no reason why it would not work on any version of MATLAB.

[Birdman]

@Stephen: But there is an improvement, right? :)

[Amitrajit Mukherjee]

Yah there is...Actually I need a versatile Code which can be used in such computers with no internet..So no option will be there to download any MATLAB function..But other options are also appreciable..

Answer 3

[Stephen23]

Download Matt Fig's excellent rcumsum and simply do this:

>> A = [0 0 1 1 0 0 0 1 1 1 1 1 0 0 0 0 1 1 1 0 0 1];
>> B = rcumsum(A);
>> B = B(B==0 | [diff(B)<0,true])
B =
   0   0   2   0   0   0   5   0   0   0   0   3   0   0   1

[Amitrajit Mukherjee]

rcumsum command is not working

[Stephen23]

@Amitrajit Mukherjee: did you download it, as you were advised to do?