How can i eliminate a few column?

i have 10 pcs of 200 by 200 dim of images. then i formed a matrix with the 10 by 40000. some of the column consist the same value from top to bottom, therefore i want to eliminate or replace it with 0. i have try repmat and std or even mean. i want to have only the significant features of my image so that i can perform PCA using princomp function.tq 4 ur help.

[Azzi Abdelmalek]

What is O ?

[maysarah sulaiman]

oh actually i typed it wrongly just now, i have amend my question.tq

Answer 1

[Image Analyst]

Try this:

% Generate sample data:
columns = 18; % Could be 40000 or size(m, 2)
rows = 4;
m = randi(4, rows, columns)

% ----- HERE'S THE MAIN CODE ---------------------------
% Find out where the entire column is the same number
% by taking the mean of the column and seeing
% if the mean of the column is the same as the first row.
columnAllTheSame = mean(m) == m(1,:)
% Set those that are all the same to 0:
m(:, columnAllTheSame) = 0

[Image Analyst]

By the way, where does image processing and segmentation (like your tags) come into all this?

[maysarah sulaiman]

because my aim to do this is to complete my image processing task. i'm sorry if i tagged wrongly.

[Image Analyst]

So did my code do what you need to do?

[maysarah sulaiman]

i have try the code, but it returns me all column 0.can u elaborate more on the codes?

[Image Analyst]

I don't understand what this means "returns me all column 0." There is no column 0 - there are columns 1 through size(m, 2). Or, are you saying that all columns are zero for every row in the column? In essence, the entire matrix is zero? I don't see how that can be. Can you give an example of the matrix you are having trouble with? My code, as always, is very well commented so I don't know how much more I can elaborate. What is confusing to you?

[maysarah sulaiman]

urm i just realize that i define it wrongly. i got it already.thanks a lot.

Answer 2

[Azzi Abdelmalek]

Use unique function

help unique

[maysarah sulaiman]

i have try but this don't give me the ans that i want. My data is actually images, therefore i still need to retain the character of each row.