How can I randomly select a row from a matrix?

I have a matrix (m) that is 17543 x 17. The values are of the type double.

I want to randomly select 1 row from this matrix and save it as a new vector.

I tried this:

mrow = m(randsample(m:17543,1),:)

This works if the values are integers but it does not work because they are doubles.

It returns the error message:

"Subscript indices must either be real positive integers or logicals."

Any help would be really appreciated.

Thanks,

Graeme

[chaitra kn]

this is for to select only first row,how can i select more than one random rows in two 2 matrix.

please help me out

Answer 1

[Evan]

Try this:

ind = ceil(rand * size(m,1));
mrow = m(ind,:);

[Graeme]

This seems to choose the first row everytime.

I changed it to:

ind = ceil(rand * size(m:17543));

mrow = m(ind,:);

It now selects the first row everytime and another random row.

Do you know how to get around this?

[Evan]

Are you sure? I just tried this out with a random sample of size 17543x17 and I'm getting different rows each time. When you run my code, does the value of "ind" always return 1? I think it would only return 1 every time if m was a 1xn matrix.

[Graeme]

Apologies you are correct.

Thanks you very much for your help!

[Evan]

No worries! And you're welcome--glad you got it fixed. :)

[Sushmita kumari]

i i wish to find a coloum insted of row .please suggest sutable code

Answer 2

[Jonathan Sullivan]

Try using randi

Example

randomRow = m(randi(size(m,1)),:);

Answer 3

[Wayne King]

m = randn(17543,17);
idx = randperm(size(m,1),1);
B = m(idx,:);

idx tells you which row you randomly selected.

If you have an older version of MATLAB where the above does not work do:

m = randn(17543,17);
idx = randperm(size(m,1),1);
B = m(idx(1),:);