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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 Cobeldick 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.

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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 Cobeldick
Stephen Cobeldick on 27 Apr 2018
Edited: Stephen Cobeldick 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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