Repeat copies of array elements: Run-length decoding in MATLAB

Question

I\'m trying to insert multiple values into an array using a \'values\' array and a \'counter\' array. For example, if:

a=[1,3,2,5]
b=[2,2,1,3]

Answer 1

There is finally (as of R2015a) a built-in and documented function to do this, repelem. The following syntax, where the second argument is a vector, is relevant here:

W = repelem(V,N), with vector V and vector N, creates a vector W where element V(i) is repeated N(i) times.

Or put another way, "Each element of N specifies the number of times to repeat the corresponding element of V."

Example:

>> a=[1,3,2,5]
a =
     1     3     2     5
>> b=[2,2,1,3]
b =
     2     2     1     3
>> repelem(a,b)
ans =
     1     1     3     3     2     5     5     5