I don't understand what this u(:,1) does to matrix or vector?

Hi

What does the following notation mean

u(:,1)

Does it covert a row vector to a column vector?

Thanks

Answer 1

[pfb]

It gives you the first column of the array u.

If u is a row vector, that is the 1st element.

if u is a column vector, that is the entire vector.

If you want to transform a row vector into a column, see u', transpose(u), or u(:).

[DM]

thanks, By array you mean a matrix right?

[pfb]

yes.

Note that u' and transpose(u) have different effects for complex numbers.

[DM]

I have also come across the following notation x(:)? Do you know what it means?

[Stephen23]

The syntax x(:) creates a column vector out of x, regardless of the shape of x. Here is some documentation and examples:

http://www.mathworks.com/help/matlab/matlab_prog/symbol-reference.html#bsgigzp-13

http://blogs.mathworks.com/loren/2006/11/10/all-about-the-colon-operator/#8