why is a blank ignored in strcat

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?

Answer 1

[Jan]

'% 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.

Answer 2

[Friedrich]

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')]

[Ross]

Thanks for that Friedrich, nearly there -- can get by -- but the expected (for me) blank in front of the 4 is still missing with both methods you've proposed.

[Image Analyst]

@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]

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]

@Image Analyst: I've inserted "@Ross" in your comment and have removed by concerning question.

Answer 3

[Jos (10584)]

This used to be my workaround for the way strcat handles spaces:

strrep(strcat('AAA', '#SPACE#', 'BBB'),'#SPACE#',' ')

[Jan]

What about: ['AAA', ' ', 'BBB'] ?

[Jos (10584)]

I should have stressed the word used ...