Combine output from for loop into one long vecor, then put that row into a cell.

Hi all,

I have this code, and it works how I would like for the first row, but I am having trouble generalizing it.

y = randi(10,10);
out = [];
m = sparse(y);
for j1 = 1:N
  y1 = (j1-1) * ones(1, m(1,j1));
  out = [out y1];
end

Thanks in advance.

Answer 1

[Star Strider]

Not certain I understand what you want, but if you want ‘out’ to be a cell array, just address it that way:

out{j1} = [out y1];

[Ellie]

I think that is along the lines of what I want to do, but not quite there.

If for example, the first row of y consists of [2 3 2], the code will then put this into a vector[0 0 1 1 1 2 2]. The code currently does this fine, but I am wanting to make it more general, to do this for rows 1:N. The problem that I am facing is that each row will be different lengths, so they need to go into a cell.

[Star Strider]

They are each different length cells. (I had to supply ‘N’.) This produces a (1x10) cell of varying-length double vectors for ‘out’:

y = randi(10,10);
N = size(y,2);
out = [];
m = sparse(y);
for j1 = 1:N
  y1 = (j1-1) * ones(1, m(1,j1));
  out{j1} = [out y1];
end

What about that doesn’t work in your application?

[Ellie]

I am not sure what about it needs to be modified, but it doesn't do what I want. The code needs to be modified in someway, although I don't know how. I have tried this, but it isn't working.

y = randi(10,10);
N = size(y,2);
out = [];
m = sparse(y);
for j1 = 1:N
    for j2 = 1:N
  y1 = (j1-1) * ones(1, m(j2,j1));
  out{j1} = [out y1];
    end
end

[Star Strider]

Well, that certainly clears things up!

What project are you working on, what do you want to do, and how do you want to do it?

[Ellie]

Well, for each row, I have a matrix which identifies the number of times an element occurs (starting with 0). For example [2 3 1] would translate to [0 0 1 1 1 2]. I need to do this for each row and I have been having trouble, because they are all different lengths.

[Star Strider]

I would use the histc (or histcounts) function to get the frequencies. It operates column-wise, and all the vectors are the same lengths. It would seem to me to be easier:

y = randi([0 10], 10);
hy = histc(y, [0:10]);

[Ellie]

I already have the frequencies. Now I need to make the corresponding number appear that many times. I explained it above.

[Star Strider]

i don’t understand. If you already have the frequencies, then you already have the vectors you want.

[Ellie]

So, I have the frequency vector [3 2 3 2]. I need to make this into [0 0 0 1 1 2 2 2 3 3].

I get what you're saying, but my code gives the frequency, and I need to have a vector like described.

[Star Strider]

This seems to work:

fv = [3 2 3 2];                                 % Frequency Vector Matrix
for k1 = 1:size(fv,1)                           % Iterate Over Rows Of ‘fv’
    V = [];                                     % Define ‘V’
    for k2 = 1:size(fv,2)                       % Iterate Over Each Column Of The ‘fv’ Row
        V = [V (k2-1)*ones(1,fv(k1,k2))];       % Concatenate ‘V’
    end
    out{k1} = V;                                % Assign ‘out’
end
celldisp(out)                                   % Display Output (Optional)

See if it does what you want.

[Ellie]

Fantastic! Thank you so much!!

[Star Strider]

My pleasure!

I’m very happy we got this sorted!