Why are complex values obtained for the below function (x) in the if condition?

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Navid
Navid 2023-11-14
编辑： Matt J 2023-11-14
Ran in:
Hi there! I'm facing an issue with the below function. The function is supposed to generate values for x that are not imaginary. However, I'm getting a warning: "Imaginary parts of complex X and/or Y arguments ignored." To be more specific, unlike the output shown in the figure, when y is equal to 0, the function should calculate x=0. Can you please assist me in finding out what could be causing this issue?
clc
close all
clear all
a = 280;
b = 580;
c = 0.35;
d =1.71E5;
e = 7;
f = 1+(3.5*(a/b));
g = d/(1+(0.002*e*(d/a)));
y = (0:2.5:b);
if any(y <= a)
x = (y/d)+(0.002*((y/a).^e));
if any(y > a)
x = 0.002+(a/d)+((y-a)/g)+(c.*(((y-a)/(b-a)).^f));
end
end
plot(x,y)
Warning: Imaginary parts of complex X and/or Y arguments ignored.
xlabel('x')
ylabel('y')

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采纳的回答

Matt J
Matt J 2023-11-14
Ran in:
Because you are raising a negative number to a fractional power, e.g.,
(-2)^1.5
ans = 0.0000 - 2.8284i
  1 个评论
Matt J
Matt J 2023-11-14
编辑：Matt J 2023-11-14
Ran in:
Perhaps,
a = 280;
b = 580;
c = 0.35;
d =1.71E5;
e = 7;
f = 1+(3.5*(a/b));
g = d/(1+(0.002*e*(d/a)));
y = (0:2.5:b);
x = (y/d)+(0.002*((y/a).^e));
r=(y>a);
x(r)= 0.002+(a/d)+((y(r)-a)/g)+(c.*(((y(r)-a)/(b-a)).^f));
plot(x,y)
xlabel('x')
ylabel('y')

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更多回答（1 个）

Torsten
Torsten 2023-11-14
Ran in:
Maybe you mean
clc
close all
clear all
a = 280;
b = 580;
c = 0.35;
d =1.71E5;
e = 7;
f = 1+(3.5*(a/b));
g = d/(1+(0.002*e*(d/a)));
y = (0:2.5:b);
x = zeros(size(y));
idx = y<=a;
x(idx) = (y(idx)/d)+(0.002*((y(idx)/a).^e));
x(~idx) = 0.002+(a/d)+((y(~idx)-a)/g)+(c.*(((y(~idx)-a)/(b-a)).^f));
plot(x,y)
xlabel('x')
ylabel('y')

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