how to select random columns?

i have a data sample named data. it contains 4601 rows with 57 column.and how can i generate random columns from the data sample?

Answer 1

[James Tursa]

If you want only one column at random:

    x = randi(size(data_sample,2));
    column = data_sample(:,x);

For more than one column (may have repeats):

    ncol = number of columns you want
    x = randi(size(data_sample,2),1,ncol);
    columns = data_sample(:,x);

For more than one column with no repeats (will error if ncol is too large):

    ncol = number of columns you want
    x = randperm(size(data_sample,2),ncol);
    columns = data_sample(:,x);

[nurul liyana]

may i know 2 stand for what? i mean (data_sample,2)

[James Tursa]

The 2 stands for the 2nd size value ... i.e., the number of columns. A 1 would have been for rows. E.g.,

>> data_sample = rand(3,5)
data_sample =
    0.3063    0.8176    0.3786    0.3507    0.5502
    0.5085    0.7948    0.8116    0.9390    0.6225
    0.5108    0.6443    0.5328    0.8759    0.5870
>> size(data_sample)
ans =
     3     5             % <-- Dimensions are 3 x 5
>> size(data_sample,1)
ans =
     3                   % <-- 1st dimension is 3
>> size(data_sample,2)
ans =
     5                   % <-- 2nd dimension is 5

[nurul liyana]

thanks a lot. i really appreciate it