XMAX must be a floating point scalar

Question

Pooyan Jafari 2020-8-5

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/575743-xmax-must-be-a-floating-point-scalar

评论： Walter Roberson 2020-8-5

clc,clear all,close all;
syms beta theta r ;
D = 10;
C = 10;
L1 = 4;
Ri = D/2 + L1;
Rbeta0 = Ri;
Rt0 = (2*L1*cos(theta) + sqrt((D^2) - (2*(L1^2)) + (2*(L1^2)*cos(2*theta))) )/2;
Rmaxtb0 = (Rt0*Rbeta0)/Ri;
Rmaxtb00 = matlabFunction(Rmaxtb0)
Vmbeta0 = (2*(pi^2)*((D+(2*L1))^2)) / ((((2*L1*pi)+(pi*D))^2));
Vbeta0 = Vmbeta0 * (1 - ((r^2) / (Rmaxtb0^2))) * r;
Vbeta00 = matlabFunction(Vbeta0)
Wsigmat = integral2(Vbeta00,0,Rmaxtb00,0,2*pi,'AbsTol',1e-5, 'RelTol',1e-5)

I got the following error:

Error using integral2 (line 76)

XMAX must be a floating point scalar.

this is the integral:

any help?

(thanks in advance)

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Answer 1

Walter Roberson 2020-8-5

1
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https://ww2.mathworks.cn/matlabcentral/answers/575743-xmax-must-be-a-floating-point-scalar#answer_475708

在 MATLAB Online 中打开

For integral2(), the limits of the second variable can be function handles, but not the limits of the first variable.

You need to change the order of integration.

Vbeta00 = matlabFunction(Vbeta0)

You are letting matlabFunction pick the order of variables for integration. Are you sure that it is going to pick the "right" order? Are readers of your code going to be sure that it is going to pick the "right" order? You should be using the 'vars' option to specify the order of variables.... And when you do, you can switch the order of variables so that you can use the functions for the limits on r

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Pooyan Jafari 2020-8-5

在 MATLAB Online 中打开

I tried this one and it is working!

am I doing right based on what you said?

Thanka alot for your kind help

clc,clear all,close all;
syms beta theta r ;
D = 10;
C = 10;
L1 = 4;
Ri = D/2 + L1;
Rbeta0 = Ri;
Rt0 = (2*L1*cos(theta) + sqrt((D^2) - (2*(L1^2)) + (2*(L1^2)*cos(2*theta))) )/2;
Rmaxtb0 = (Rt0*Rbeta0)/Ri;
Rmaxtb00 = matlabFunction(Rmaxtb0)
Vmbeta0 = (2*(pi^2)*((D+(2*L1))^2)) / ((((2*L1*pi)+(pi*D))^2));
Vbeta0 = Vmbeta0 * (1 - ((r^2) / (Rmaxtb0^2))) * r;
Vbeta00 = matlabFunction(Vbeta0,'Vars',[theta r])
Wsigmat = integral2(Vbeta00,0,2*pi,0,Rmaxtb00,'AbsTol',1e-5, 'RelTol',1e-5)