what does this Complex values are not supported mean?

Question

Juan José Martinez Parra 2021-8-23

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1438939-what-does-this-complex-values-are-not-supported-mean

评论： Juan José Martinez Parra 2021-8-23

errors in line 35 "xlim([min(tetagrados) max(tetagrados)])"

clear variables
clc
close all
MasaCarga = 400;
M = MasaCarga/2;
L = 1.4;
L1 = 0.5;
L2 = 1;
a = 0.8;
b = 2.5;
g = 9.8;
teta1 = acos((b-L1)/L);
teta2 = acos((b-L2)/L);
nDivisiones = 100;
teta = linspace(teta1,teta2,nDivisiones);
N = M*g*a./(L*cos(teta));
Ey = M*g*a./(L*cos(teta));
Dy = M*g*(1-a./(L*cos(teta)));
Fp = M*g*cot(teta);
Cy = M*g*(1-2*a./(L*cos(teta)));
Cx = -Fp;
Fy = M*g*(1-a./(L*cos(teta)));
Fx = -Fp;
tetagrados = teta*180/pi;
colorazul = [0 0 153]/255;
colorvino = [153 51 102]/255;
plot(tetagrados,Fp,'linewidth',1.2,'displayname','Fuerza F_(p)','color',colorazul);
xlim([min(tetagrados) max(tetagrados)])
xlabel('Angulo \alpha (°)')
ylabel('Fuerza (N)')
hold on
plot(tetagrados,N,'r','linewidth',1.2,'displayname','Fuerza N','color',colorvino);
legend('boxoff')
legend('location','best')
set(gca,'fontsize',13)
figure()
plot(tetagrados,Ey,'linewidth',1.2,'displayname','Fuerza E_y','color',colorazul);
xlim([min(tetagrados) max(tetagrados)])
xlabel('Angulo \alpha (°)')
ylabel('Fuerza (N)')
hold on
plot(tetagrados,Dy,'r','linewidth',1.2,'displayname','Fuerza D_(y)','color',colorvino);
legend('boxoff')
legend('location','best')
set(gca,'fontsize',13)
figure()
plot(tetagrados,Cx,'linewidth',1.2,'displayname','Fuerza C_(x)','color',colorazul);
xlim([min(tetagrados) max(tetagrados)])
xlabel('Angulo \alpha (°)')
ylabel('Fuerza (N)')
hold on
plot(tetagrados,Cy,'r','linewidth',1.2,'displayname','Fuerza C_(y)','color',colorvino);
legend('boxoff')
legend('location','best')
set(gca,'fontsize',13)

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Answer 1

Yazan 2021-8-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1438939-what-does-this-complex-values-are-not-supported-mean#answer_772804

在 MATLAB Online 中打开

tetagrados is a vector of complex numbers. So, first of all, notice that the function plot throws a warning and plots only the real parts, ignoring the imaginary ones.

Second, in this line

xlim([min(tetagrados) max(tetagrados)])

You are asking Matlab to restrict the limits of the X-axis to the min and max of tetagrados. However, tetagrados is complex, the min and max functions will return complex numbers. How can you set the limits of an axis with complex numbers? You obviously can not. So, you have an error. You should decide to work with the real part, imaginary part, or absolute values.

example:

xlim([min(real(tetagrados)) max(real(tetagrados))])