repelem substitute for older matlab version

Hi,

I want to do the following (what usually repelem does, however an older version of Matlab does not seem to have it):

Given vector a = [3 45 6 ];

I would want for instance its first element to be repeated 2 times, the second 4 times, the third element once (just as an example). So we would end up with:

aNew = [3 3 4 45 45 45 6 6];

How can that be done in a systematic way without repelem?

Thanks

[Stephen23]

You say that you want "the third element once", but it appears twice in your example. Which is correct? Where does that 4 come from?

Answer 1

[Stephen23]

>> A = [3,45,6];
>> R = [2,4,1];
>> cell2mat(arrayfun(@(a,r)repmat(a,1,r),A,R,'uni',0))
ans =
     3     3    45    45    45    45     6

[KSSV]

+1

Answer 2

[KSSV]

a = [3 45 6 ];
aNew = [3 3 45 45 45 45 6 6];
R = [2 4 3] ;
iwant = [] ;
for i = 1:length(R)
    iwant = [iwant ones(1,R(i))*a(i)] ;
end

[Stephen23]

Expanding arrays within loops is not recommended:

https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html

See my answer for a one-line solution that does not expand arrays inside loops.

[KSSV]

a = [3 45 6 ];
aNew = [3 3 45 45 45 45 6 6];
R = [2 4 3] ;
iwant = cell(1,length(R)) ;
for i = 1:length(R)
    iwant{i} = ones(1,R(i))*a(i) ;
end
iwant = [iwant{:}]