CODEWITHSUNDEEP
matlabstring-formatting
Jim
Jim

Reputation: 5960

How do you format complex numbers for text output in matlab

I have a complex number that I want to output as text using the fprintf command. I don't see a formatspec for complex numbers. Is there an easy way to do this?

Using the format spec for fixed-point is only outputting the real part.

Upvotes: 9

Views: 11492

Answers (3)

Mohsen Nosratinia
Mohsen Nosratinia

Reputation: 9864

According to the documentation of fprintf and sprintf

Numeric conversions print only the real component of complex numbers.

So for a complex value z you can use this

sprintf('%f + %fi\n', z, z/1i)

for example

>> z=2+3i; 
>> sprintf('%f + %fi\n', z, z/1i)
2.000000 + 3.000000i

You can wrap it in an anonymous function to get it easily as a string

zprintf = @(z) sprintf('%f + %fi', z, z/1i)

then

>> zprintf(2+3i)

ans =

2.000000 + 3.000000i

Upvotes: 7

Oleg
Oleg

Reputation: 10676

Address the real and imaginary parts separately:

x = -sqrt(-2)+2;
fprintf('%7.4f%+7.4fi\n',real(x),imag(x))

or convert to string first with num2str()

num2str(x,'%7.4f')

Upvotes: 6

Andrey Rubshtein
Andrey Rubshtein

Reputation: 20915

I don't know if there is an easy way, but you can write your own format function (the hard way):

function mainFunction()
    st = sprintfe('%d is imaginary, but %d is real!',1+3i,5);
    disp(st);

    st = sprintfe('%f + %f = %f',i,3,3+i);
    disp(st);
end

function stOut = sprintfe(st,varargin) %Converts complex numbers.
    for i=1:numel(varargin)
        places = strfind(st,'%');
        currentVar = varargin{i};
        if isnumeric(currentVar) && abs(imag(currentVar))> eps
            index = places(i);
            formatSpecifier = st(index:index+1);
            varargin{i} = fc(currentVar,formatSpecifier);
            st(index+1) = 's';
        end
    end
    stOut = sprintf(st,varargin{:});
end

function st = fc(x,formatSpecifier)
    st = sprintf([formatSpecifier '+' formatSpecifier 'i'],real(x),imag(x));
end

This solution suffers from some bugs, (does not handle %2d,%3f) but you get the general idea.

Here are the results:

>> mainFuncio
1+3i is imaginary, but 5 is real!
0.000000+1.000000i + 3.000000 = 3.000000+1.000000i

Upvotes: 1

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