Loop putting information into a new variable matrix

Problem: Assigning information into new variables using an if statement.

channel_number is a nx1 array that could have any value of 1,2,3,4,5. If overall there are three channels then it will have a pattern of 1,2,3,1,2,3,1,2,3,...etc. if it has 5 channels it will be 1,2,3,4,5,1,2,3,4,5,1,2,3,4,5,...etc.

pixel_info is a nx1 array where n is the same as in channel_number. It contains pixel information for images.

I want to make matrices based on the channel number that contains the pixel information

x=1;
while x<length(channel_number)+1
    if channel_number(x)==1
        channel1=pixel_info(x);
    elseif channel_number(x)==2
        channel2=pixel_info(x);
    elseif channel_number(x)==3
        channel3=pixel_info(x);
    elseif channel_number(x)==4
        channel4=pixel_info(x);
    elseif channel_number(x)==5
        channel5=pixel_info(x);
    else
        disp('error');
    end
    x=x+1
end

I tried creating matrixes for the channels, which kind of gave me what I wanted. Except it would give me a value and an empty cell and a value and an empty cell. Also it was a horizontal array. I would prefer a vertical one.

x=1;
while x<length(channel_number)+1
    if channel_number(x)==1
        channel1(x)=pixel_info(x);
    elseif channel_number(x)==2
        channel2(x)=pixel_info(x);
    elseif channel_number(x)==3
        channel3(x)=pixel_info(x);
    elseif channel_number(x)==4
        channel4(x)=pixel_info(x);
    elseif channel_number(x)==5
        channel5(x)=pixel_info(x);
    else
        disp('error');
    end
    x=x+1
end

So overall, I'm just looking for a way to read information into new variables for image analysis.

Any help is greatly appreciated

Answer 1

[Ben11]

Since pixel_info is a cell array you might want to use curly braces {} to access the information it contains, so you would not get a cell array as output. Also if you want a vertical array you can take the transpose:

pixel_info = pixel_info';

Answer 2

[Star Strider]

One way to do this is to create empty vectors at the outset and then simply concatenate new values onto them:

channel1 = [];
channel2 = [];
channel3 = [];
channel4 = [];
channel5 = [];
x = 1;
while x<length(channel_number)+1
    if channel_number(x)==1
        channel1 = [channel1; pixel_info(x)];
    elseif channel_number(x)==2
        channel2 = [channel2; pixel_info(x)];
    ...
end

This also creates column vectors out of them.