For loop with two conditions

I need to create a for loop that runs from n=-2 to 2. When n=0, I must use a different equation (D_n_0) to plot the result. When n=-2,-1,1,2 I will use another equation (D_n) to plot the result.

How do I set up a foot loop that allows for a different equation when n=0 but not for other values?

Thank you!

[Dyuman Joshi]

You can use if, elseif, else conditions to check the value and the plot accordingly.

Can you specify the equations that you need to plot?

Answer 1

[Voss]

for n = -2:2
    if n == 0
        % use D_n_0
    else
        % use D_n
    end
end

[Yamana Uno]

t = 0:0.8;

for n = -2:2

if n == 0

D_n_0 = 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));

xt0 = (D_n_0).*(exp(7.8539.*1j.*n.*t));

subplot(2,1,2)

plot(t,xt0)

hold on

else

D_n = 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 = (D_n).*(exp(7.8539.*1j.*n.*t));

plot(t,xt)

hold off

title('Exponential Fourier Series')

end

end

This is what I have so far. I'm not sure what is incorrect but I cannot get this to plot and the command window says imginary parts of complex X and Y ignored. Is that the issue?

[Voss]

t is a scalar, so you're only ever plotting one point each time, which you won't see without a data marker. Check that the t I used below is something like you intended.

hold off in the else block makes subsequent plotted lines replace what was already plotted, so I changed it to hold on.

hold on in the if block is not necessary because that block is only executed one time (when n == 0), so only one line is being plotted, so I removed that (and I assumed that plot should be in another subplot).

"the command window says imginary parts of complex X and Y ignored"

For plotting complex numbers you may want to plot the magnitude and phase separately.

t = linspace(0,0.8,100);
for n = -2:2
    if n == 0
        D_n_0 = 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));
        xt0 = (D_n_0).*(exp(7.8539.*1j.*n.*t));
        subplot(2,1,2)
        plot(t,xt0)
    else 
        D_n = 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 = (D_n).*(exp(7.8539.*1j.*n.*t));
        subplot(2,1,1)
        plot(t,xt)
        hold on
        title('Exponential Fourier Series')
    end
end

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

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

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

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