creating a vector that repeats a number 360 times

i want a way to create a vector that repeats the same number 360 times lets say my number is 500 and i want the vector to look like this...

[500; 500; 500; 500; ....]

Answer 1

[dpb]

A zillion different ways to do this--just a few of the more obvious are

v=500+zeros(360,1);
v=500*ones(360,1);
v=repmat(500,360,1);

use your imagination...

Answer 2

[Jan]

And:

c = 500;
v = c(ones(360, 1));

Or:

v(1:360, 1) = 500;

[EDITED]

v = zeros(360, 1);
v(:) = 500;

[Image Analyst]

I never would have thought of the first one. Unexpected. The second one is a neat trick that should be more well known.

[Jan]

@Image Analyst: The 1st method is an inlined repmat(500, 360, 1).

For beginners it is important to mention, that it fails when v exists before and is larger or has another type. But even experienced programmers can fail, e.g. when a piece of code is inserted by copy&paste. Therefore I avoid it.

[Roberto]

Great contribution!!!

Answer 3

[Roberto]

r = ones(1,360)*500 % row vector
c = ones(360,1)*500 % column vector

[Image Analyst]

Note: ones(1,360) is a row vector, not a column vector like the poster asked for.

[Roberto]

my mistake.. :(

Answer 4

[Image Analyst]

Try this

columnVector = 500 * ones(360, 1);

[Sean de Wolski]

I'd expect addition o be faster than multiplication.

zeros(360,1)+500

[dpb]

On modern Intel FPP, I believe they're the same for FMUL and FADD. FDIV is still an order of magnitude kind of difference.

OTOH, w/ the JIT optimizer, wouldn't surprise me terribly if for a constant it didn't do either but simply translated to a memset() or similar copy, anyway. I suppose for floating point values that's less likely, but who knows how clever they've gotten??? :)

Would definitely have to do timings to confirm if were any difference and then TMW would say to not base code on the results of that for any given release as the guts can always (and do) change.

Answer 5

[Pradeep Punniyakotti]

You can try this.

linspace(500,500,360)

The number 500 will be repeated 360 times. The answer will be a column vector.

Take transpose to get row vector.