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sprintf: how to efficiently create a string of 75 numbers, separated by comma

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Abhinav
Abhinav on 27 Apr 2018
Edited: Stephen on 27 Apr 2018
I have an array which contains 75 numeric elements. I want to write these numbers as a string separated by a comma. If there were few numbers, I could use 'sprintf' as follows:
A=[1,2];
str=sprintf('%d,%d',A(1:end));
I need an efficient way to do it when there are many entries in A.

Accepted Answer

Star Strider
Star Strider on 27 Apr 2018
You can still use sprintf. You just need to create a ‘dynamic’ format string:
A = 1:5;
str = sprintf([repmat('%d,',1, numel(A)-1), '%d'], A)
str =
'1,2,3,4,5'
That will adapt for any ‘A’ vector.

More Answers (2)

Ameer Hamza
Ameer Hamza on 27 Apr 2018
Edited: Ameer Hamza on 27 Apr 2018
This will work.
strjoin(string(A), ',')

Stephen
Stephen on 27 Apr 2018
Edited: Stephen on 27 Apr 2018
"I need an efficient way to do it when there are many entries in A."
This is probably about the most efficient way:
A = 1:5;
str = sprintf(',%d',A);
str = str(2:end);
Timing comparisons for 1e4 iterations:
Elapsed time is 0.539053 seconds. % this answer.
Elapsed time is 2.54425 seconds. % Star Strider's answer.

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