Why do I get "Array indices must be positive integers or logical values" error?

Question

Arif Najmi 2023-1-30

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https://ww2.mathworks.cn/matlabcentral/answers/1902835-why-do-i-get-array-indices-must-be-positive-integers-or-logical-values-error

回答： Askic V 2023-1-30

lc= 0.03

b=0.013

Rc= 0.0275

theta1= 0:15:360

theta2=theta1*pi/180

x=lc/2;

y=((Rc^2)*(theta2))

z=((b^2)*0.5)*(sin((theta1).*2))

r=b*(sin(theta1))

u1=Rc^2

u2=r.^2

u=r.*(((u1)-(u2)).^1/2)

rr=Rc^2*atan(r/u)

Vc=x(y+z-u-rr)

Why can't solve? Can someone help me?

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Answer 1

Arif Hoq 2023-1-30

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https://ww2.mathworks.cn/matlabcentral/answers/1902835-why-do-i-get-array-indices-must-be-positive-integers-or-logical-values-error#answer_1159155

在 MATLAB Online 中打开

try this:

lc= 0.03;
b=0.013;
Rc= 0.0275;
theta1= 0:15:360;
theta2=theta1*pi/180;
x=lc/2;
y=((Rc^2)*(theta2));
z=((b^2)*0.5)*(sin((theta1).*2));
r=b*(sin(theta1));
u1=Rc^2;
u2=r.^2;
u=r.*(((u1)-(u2)).^1/2);
rr=Rc^2*atan(r/u);
Vc=x*(y+z-u-rr)
Vc = 1×25
1.0e-04 *

   -0.1782   -0.1614   -0.1220   -0.0783   -0.0518   -0.0384   -0.0107    0.0362    0.0710    0.0868    0.1066    0.1463    0.1909    0.2132    0.2268    0.2592    0.3043    0.3381    0.3521    0.3732    0.4169    0.4576    0.4786    0.4937    0.5271

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Answer 2

Askic V 2023-1-30

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1902835-why-do-i-get-array-indices-must-be-positive-integers-or-logical-values-error#answer_1159180

在 MATLAB Online 中打开

You asked why, and the answer is because of this line:

Vc=x(y+z-u-rr)

here, x is considered an array and y+z-u-rr is an index. basically you're trying to access an element of the array throught its index. Indices should be positive integers or logical values and not numbers with decimal points.

So this is probably a typo and Arif corrected this line to be:

Vc=x*(y+z-u-rr)