Convert Integer Array to String Array where repeated integers use "R" for repeated entries

The question is a bit vague. An example will make this much more clear. Lets say I have the integer array A

 A= [ 1 1 1 1 2 2
      2 2 2 2 2 2
      3 3 3 2 3 3];

My goal is to have the following array B (it can be character/cell/string) the only requirement is that I can then write B to a text file using fprintf.

   B= '1 3R 2 7R 3 2R 2 3 1R';

Where "nR" repeats the preceding entry n times. I am going to be performing this on a large integer array (~ 5.0E+7 elements) so efficiency is crucial.

Thank you for your time.

Answer 1

[Alfredezeo]

no ideas?

Answer 2

[Walter Roberson]

https://www.mathworks.com/matlabcentral/fileexchange/41813-runlength

sprintf('%g %dR ', [values(:), counts(:)-1].' )

or if you are sure that values and counts are row vectors,

sprintf('%g %dR ', [values; counts-1]);

Answer 3

[Alfredezeo]

Worked like a charm! Thank You Walter