Using fprintf for complex numbers

Hi, I have

Z1= sqrt(3) * exp((pi*i)/4)
Z2= 2 * exp((pi*i)/6)
Z3= sqrt(3) * exp((3*pi*i)/4)
Z4= 2 * exp(pi*i)
Z5= 2 * exp(-pi*i)

And I would like something like

        Real        Complex
Z1  1.2247 + 1.2247i
Z2 1.7321 + 1.0000i
Z3 -1.2247 + 1.2247i
Z4  -2.0000 + 0.0000i
Z5 -2.0000 - 0.0000i

Using fprintf, I would think...

Thanks for your help!

Answer 1

[KALYAN ACHARJYA]

One Way:

Z1= sqrt(3) * exp((pi*i)/4)
fprintf('%f + %fi',real(Z1),imag(Z1))

More:

Z1= sqrt(3) * exp((pi*i)/4);
Z2= 2 * exp((pi*i)/6);
Z3= sqrt(3) * exp((3*pi*i)/4);
Z4= 2 * exp(pi*i);
Z5= 2 * exp(-pi*i);
disp('     Real   Complex')
fprintf('\nZ1  %.4f + %.4fi',real(Z1),imag(Z1));
fprintf('\nZ2  %.4f + %.4fi',real(Z2),imag(Z2));
fprintf('\nZ3  %.4f + %.4fi',real(Z3),imag(Z3));
fprintf('\nZ4  %.4f + %.4fi',real(Z4),imag(Z4));
fprintf('\nZ5  %.4f + %.4fi',real(Z5),imag(Z5));

Result:

[Savannah Roemer]

You're the real MVP!

Thanks so much!

S

[KALYAN ACHARJYA]

No Savannah, those MPVs are my Guru here.. continually they are teaching me .

Specially @Walter Roberson, @Image Analyst @Madhan @Jan .and...many more....

Anyway thanks for your kind words!

Answer 2

[Adam Danz]

Another alternative is to use num2str which supports conversion of complex numbers to strings.

a = -2*sqrt(-3)+5/3

a = 1.6667 - 3.4641i

num2str(a)

ans = '1.6667-3.4641i'

num2str(a, 2)  % specify precision

ans = '1.7-3.5i'

You would enter this as a string in fprintf

ijstr = num2str(a,3); 
fprintf('%s %s', 'Z1', ijstr)

Z1 1.67-3.46i

Note that this method may return strings in undesired formats such as,

num2str(160, 2)

ans = '1.6e+02'

[marcel hendrix]

p = [  9.542130347090435e-01 + 1.371703909876786e-01i
       9.542130347090435e-01 - 1.371703909876786e-01i ];
fprintf(1,'%s ',num2str(p,10));
>> 00..99554422113300334477+-00..113377117700339911ii 

What went wrong here?

[Les Beckham]

I'm not sure I can explain exactly why it does that, other than it appears to be pulling the characters out of the output of num2str by going down the columns of the 2x25 char array.

p = [  9.542130347090435e-01 + 1.371703909876786e-01i
       9.542130347090435e-01 - 1.371703909876786e-01i ];
num2str(p, 10)

ans = 2x25 char array
    '0.9542130347+0.137170391i'
    '0.9542130347-0.137170391i'

fprintf('%s ', num2str(p,10)); % << note that you don't need the "1," stdout (1) is the default

00..99554422113300334477+-00..113377117700339911ii 

One way to get what you probably want is this

c = compose('%s', num2str(p,10))

c = 2x1 cell array
    {'0.9542130347+0.137170391i'}
    {'0.9542130347-0.137170391i'}

fprintf('%s\n', c{:})

0.9542130347+0.137170391i
0.9542130347-0.137170391i

[Walter Roberson]

it appears to be pulling the characters out of the output of num2str by going down the columns of the 2x25 char array.

That is exactly what it is doing. fprintf() always follows down the columns of the first parameter, completely using up the first parameter before going on to follow down the columns of the second parameter, and so on. To put it another way: fprintf() uses linear indexing order of each parameter.

p = [  9.542130347090435e-01 + 1.371703909876786e-01i
       9.542130347090435e-01 - 1.371703909876786e-01i ];
fprintf('%s ', num2str(p,10).');

0.9542130347+0.137170391i0.9542130347-0.137170391i 

Note: careful examination will show that the blank from the format is at the end of the output only. This is due to the way that char() arrays are processed.

[marcel hendrix]

Thanks, I was on the verge of submitting a bug report...

Processing matrix arguments by column has another surprise: if one prints a matrix to a file for subsequent processing in another program, the matrix will look transposed to the post-processor. I can say from experience that this bug (in the post-processor and caused by the reverse side of the keyboard) can be very hard to find ...

[Walter Roberson]

Note that you can avoid the c{:} step if you pass compose a string scalar format instead of a character vector format.

p = [  9.542130347090435e-01 + 1.371703909876786e-01i
       9.542130347090435e-01 - 1.371703909876786e-01i ];
c = compose("%s", num2str(p,10))

c = 2x1 string array
    "0.9542130347+0.137170391i"
    "0.9542130347-0.137170391i"

fprintf('%s\n', c)

0.9542130347+0.137170391i
0.9542130347-0.137170391i

And that leads to the more compact

fprintf('%s\n', compose("%s", num2str(p,10)))

0.9542130347+0.137170391i
0.9542130347-0.137170391i

Answer 3

[Walter Roberson]

fprintf() always ignores imaginary components of numbers. You need to ask to output the real() and imaginary() components separately,

fprintf('%2s %7.4f %+7.4fi\n', 'Z1', real(Z1), imag(Z1))