Concatenate vectors in a specific, non-serial ordering

Question

I have vectors a,b and c; vectors a and b contain integer numbers while vector c has binary values as elements: (0,1).

Vector a has length n and vector b has length k. Vector c has length n+k.

I want to concatenate vectors a and b based on vector c.

For example. If c=[1 0 0 1 0 . . . . ] then I want to create vector res=[a(1) b(1) b(2) a(2) b(3) . . . ].

Is there any way to do so without a for loop?

score 7 · Accepted Answer · edited May 23 '17 at 12:15

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res = c; %// copy c for the result vector
res(c) = a;
res(~c) = b;

using logical indexing! This works because the number of 0 elements in c is exactly equal to the number of elements in b and the number of 1 elements equals the number of elements in a. Logical operators for indexing thanks to @Dan's comment

edited May 23 '17 at 12:15

Community

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answered Jan 13 '16 at 10:35

Adriaan

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This is the simplest way to do it by far. – GameOfThrows Jan 13 '16 at 10:38
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if `c` is a logical matrix to begin with you can even just do `res(c) = a` and `res(~c) = b`. – Dan Jan 13 '16 at 11:00

Concatenate vectors in a specific, non-serial ordering

1 Answers1