How can I generate values randomly from another existing vecor?

Hi everyone My problem is I want to generate a vector of values from other vector with zeros For example My vector is v1=[122,34,20,5,21] The new vector that I want to get is like that: V2=[122,0,20,0,0,5]

Answer 1

[J. Alex Lee]

how about

v1 = [122,34,20,5,21]

v1a = [0,v1]
N = numel(v1a)

ridx = randi(N,size(v1))

v2 = v1a(ridx)

[Mira le]

Is there other solution?, this one doesn't work with a long vector

[J. Alex Lee]

how does it fail?

[Steven Lord]

Looking at the error message you posted in your other message I suspect your v1 vector is actually a column vector, not a row vector.

v1 = [1, 2, 3]

v1 = 1×3

1 2 3

v1a = [0, v1]

v1a = 1×4

0 1 2 3

v2 = [1; 2; 3]

v2 = 3×1

1 2 3

v2a = [0; v2]

v2a = 4×1

0 1 2 3

v2bWILLNOTWORK = [0, v2]

Error using horzcat
Dimensions of arrays being concatenated are not consistent.

In v2bWILLNOTWORK, 0 has 1 row and v2 has 3 rows. You can't put them side-by-side in a vector but you can stack them on top of one another as shown with v2a. Compare with v1a, where both 0 and v1 had 1 row and so could be stored side-by-side.

If I'd written v1a with [0; v1] that wouldn't have worked since 0 and v1 don't have the same number of columns.