Unable to convert expression into double array

Question

Tommaso Attili 2019-2-7

1
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https://ww2.mathworks.cn/matlabcentral/answers/443703-unable-to-convert-expression-into-double-array

回答： Bo Zhang 2020-11-18

When I run my code, I keep getting this error: "The following error occurred converting from sym to double: Unable to convert expression into double array."

r=50; 
d=50;
a=12.61; 
syms x
syms y
J=(besselj(0,x*y*a/d))*((1-y^2)^0.5)*y;
B1=int(J, y, [0 1]);
E1=zeros(1,301);
t=0:0.1:30;
for i=1:301
    B=B1*besselj(0,x*r/d)*((x*tanh(x))^0.5)*sin((((9.81/d*t(i)^2)*x)*tanh(x))^0.5)*x;
    E1(i)=vpaintegral(B, x, [0 2000])
end

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Answer 1

Areej Varamban Kallan 2019-2-7

4
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https://ww2.mathworks.cn/matlabcentral/answers/443703-unable-to-convert-expression-into-double-array#answer_359968

编辑：Areej Varamban Kallan 2019-2-7

在 MATLAB Online 中打开

Hi Tommaso,

The variable E1 is defined to be a 'double' array outside the foor loop. The variable B is of symbolic type. In the for loop you are attempting to assign each element of a 'double' array to a symbolic object, which is not correct. Redefine E1 as:

E1 = sym(zeros(1,301));