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why is a blank ignored in strcat

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Ross
Ross on 15 Oct 2013
Commented: Jos (10584) on 15 Oct 2013
as an example, the following code:
strcat(num2str(1,'%02.0f'), '-', num2str(2), ' ', num2str(3), ':', num2str(4,'% 2.0f'))
produces:
01-23:4
whereas I want:
01-2 3: 4
Seems pretty simple but ... would someone help please?

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Accepted Answer

Jan
Jan on 15 Oct 2013
Edited: Jan on 15 Oct 2013
'% 2.0f' adds a leading space on demand only, so you want: ' %2.0f'.
But this would be nicer, faster and less confusing:
sprintf('%02.0f-%d %d: % 2.0f', 1, 2, 3, 4)
To get around this ugly space gimmicks, which come from the backward compatibility to times before cell strings have been invented, I'm using a dedicated function to join strings: FEX: CStrCatStr. But this is designed for cell strings and for strings horzcat works sufficiently without deleting spaces smartly.

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More Answers (2)

Friedrich
Friedrich on 15 Oct 2013
Hi,
the doc states:
"For character array inputs, strcat removes trailing ASCII white-space characters: space, tab, vertical tab, newline, carriage return, and form-feed. For cell array inputs, strcat does not remove trailing white space."
So you can use:
strcat({num2str(1,'%02.0f')}, {'-'},{num2str(2)}, {' '}, {num2str(3)}, {':'}, {num2str(4,'% 2.0f')})
or dont use strcat and use []:
[num2str(1,'%02.0f'), '-', num2str(2), ' ', num2str(3), ':', num2str(4,'% 2.0f')]

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Image Analyst
Image Analyst on 15 Oct 2013
@Ross: I'm not understanding why you want these crazy complicated ways when the sprintf() Jan suggested is so much more simpler and reliable. I always use sprintf() since I found out what you're finding out now. I suggest you follow Jan's and my recommendations to use sprintf and avoid these problems and simplify your code.
Image Analyst
Image Analyst on 15 Oct 2013
I was talking to Ross. I know Frederich knows both methods and I agree with you about why Frederich answered that way. I was trying to point Ross towards the method that I find gives me much more control with much less complicated syntax.
Jan
Jan on 15 Oct 2013
@Image Analyst: I've inserted "@Ross" in your comment and have removed by concerning question.

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Jos (10584)
Jos (10584) on 15 Oct 2013
Edited: Jos (10584) on 15 Oct 2013
This used to be my workaround for the way strcat handles spaces:
strrep(strcat('AAA', '#SPACE#', 'BBB'),'#SPACE#',' ')

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Jan
Jan on 15 Oct 2013
What about: ['AAA', ' ', 'BBB'] ?
Jos (10584)
Jos (10584) on 15 Oct 2013

I should have stressed the word used ...

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