creating a vector that repeats a number 360 times
307 views (last 30 days)
Show older comments
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; ....]
0 Comments
Answers (5)
dpb
on 9 May 2014
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...
0 Comments
Jan
on 10 May 2014
Edited: Jan
on 10 May 2014
And:
c = 500;
v = c(ones(360, 1));
Or:
v(1:360, 1) = 500;
[EDITED]
v = zeros(360, 1);
v(:) = 500;
3 Comments
Jan
on 10 May 2014
@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
on 9 May 2014
Edited: Roberto
on 22 May 2014
r = ones(1,360)*500 % row vector
c = ones(360,1)*500 % column vector
2 Comments
Image Analyst
on 10 May 2014
Note: ones(1,360) is a row vector, not a column vector like the poster asked for.
Image Analyst
on 9 May 2014
Try this
columnVector = 500 * ones(360, 1);
2 Comments
Sean de Wolski
on 22 May 2014
I'd expect addition o be faster than multiplication.
zeros(360,1)+500
dpb
on 22 May 2014
Edited: dpb
on 22 May 2014
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.
Pradeep Punniyakotti
on 27 Mar 2018
Edited: Pradeep Punniyakotti
on 27 Mar 2018
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.
0 Comments
See Also
Categories
Find more on Historical Contests in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!