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Avoid +0 when using fprintf %+d

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giannit
giannit on 1 Jun 2020
Commented: giannit on 1 Jun 2020
Consider the code
names={'aba','cda','efa','fea','pod'};
numbers=randi([-1 1],5,4);
for i=1:5
fprintf('|%s|%+d|%+d|%+d|%+d|\n',names{i},numbers(i,:))
end
whose output is similar to
|aba|+0|+1|+1|+1|
|cda|-1|+1|-1|+1|
|efa|+1|+0|-1|-1|
|fea|+1|+0|-1|+1|
|pod|+1|-1|-1|-1|
Is there a way to remove the plus in front of the 0s, or to not print + when the number is 0?

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Accepted Answer

dpb
dpb on 1 Jun 2020
Edited: dpb on 1 Jun 2020
Not w/o some code logic of one form or the other, no. There is no "magic bullet" format descriptor that behaves as desired; as you notice, the '+' adds the sign to any numeric field. There also is no conditional formatting expression built in like an Excel format expression.
You could, however, build the format string dynamically and insert the plus only where the values aren't zero. Or, (in a somewhat less elegant solution imo) you could write the output string to a variable first and then do character substitution on it before displaying or writing to file or whatever it is that is the end objective.
The latter is, of course, a trivial change to implement even if somewhat klunky--
for i=1:5
str=sprintf('|%s|%+d|%+d|%+d|%+d|\n',names{i},numbers(i,:));
fprintf('%s\n',strrep(str,'+0',' 0'))
end
Let's see on the former...scratch, stratch...emmm....ah! OK, here, try this:
>> fmts={'% d|','%+d|'};
>> disp(cell2mat([compose('|%s|',string(names.')) compose(fmts((numbers~=0)+1),numbers)]))
|aba|+1|+1|-1|+1|
|cda|-1|+1| 0| 0|
|efa|+1|-1| 0|+1|
|fea|-1| 0|-1| 0|
|pod|+1| 0| 0|-1|
>>

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giannit
giannit on 1 Jun 2020
Thank you for both solutions!

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