Finding sum of for loop with if else statement

trangeF = 0:0.001:1.6; % Time range

init = 0;

for n = -2:2

if n == 0

s0 = 312.5.*((-0.08481.*1j.*exp(-0.08481.*1j.*n)/-7.8539.*1j.*n)-((-7.8539.*1j.*n)/(-61.6837.*(n^2)+400)).*(exp(-0.08481.*1j.*n)-1));

xt = (s0).*(exp(7.8539.*1j.*n.*trangeF));

else

s1 = 312.5.*(((exp(-0.08481.*1j.*n)-1)/-7.8539.*1j.*n)-(((-7.8539.*1j.*n)/(-61.6837.*(n^2)+400)).*(exp(-0.08481.*1j.*n)-1)));

xt = (s1).*(exp(7.8539.*1j.*n.*trangeF));

end

end

sums = init + xt;

plot(trangeF, sums,'b')

I am trying to find the sum of the loop. I know I am supposed to have a variable that initializes to 0, then each time I step thrpugh the loop, I add the term to the initialized variable. Am I setting this up correctly?

Answer 1

[Fabio Freschi]

You must

1. move your sum inside the loop
2. increment your summation variable

Note that your vector is complex and plot displays only the real part

trangeF = 0:0.001:1.6; % Time range

% initialization
sums = zeros(size(trangeF));

for n = -2:2
    if n == 0
        s0 = 312.5.*((-0.08481.*1j.*exp(-0.08481.*1j.*n)/-7.8539*1j)-((-7.8539.*1j.*n)/(-61.6837.*(n^2)+400)).*(exp(-0.08481.*1j.*n)-1));
        xt = (s0).*(exp(7.8539.*1j.*n.*trangeF));
    else
        s1 = 312.5.*(((exp(-0.08481.*1j.*n)-1)/-7.8539.*1j.*n)-(((-7.8539.*1j.*n)/(-61.6837.*(n^2)+400)).*(exp(-0.08481.*1j.*n)-1)));
        xt = (s1).*(exp(7.8539.*1j.*n.*trangeF));
    end
    
    % sum in the loop
    sums = sums + xt;
end

figure
plot(trangeF, sums,'b')

Warning: Imaginary parts of complex X and/or Y arguments ignored.

Answer 2

[Torsten]

You mean this ?

trangeF = 0:0.001:1.6; % Time range 
xt = zeros(size(trangeF));
for n = -2:2
    if n == 0
        s0 = 312.5.*((-0.08481.*1j.*exp(-0.08481.*1j.*n)/-7.8539*1j)-((-7.8539.*1j.*n)/(-61.6837.*(n^2)+400)).*(exp(-0.08481.*1j.*n)-1));
        xt = xt + (s0).*(exp(7.8539.*1j.*n.*trangeF));
    else 
        s1 = 312.5.*(((exp(-0.08481.*1j.*n)-1)/-7.8539.*1j.*n)-(((-7.8539.*1j.*n)/(-61.6837.*(n^2)+400)).*(exp(-0.08481.*1j.*n)-1)));
        xt = xt + (s1).*(exp(7.8539.*1j.*n.*trangeF));
    end
end
plot(trangeF, [real(xt);imag(xt)],'b')