"??? Undefined function or method 'int' for input arguments of type 'double'."

Question

Shing 2013-1-12

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/58604-undefined-function-or-method-int-for-input-arguments-of-type-double

Hi all,

I have been trying to solve this problem. To set up a e array[200 by 200] to create some mesh beam diagram. ' However,I keep on receiving this error message:

"??? Undefined function or method 'int' for input arguments of type 'double'." on the integration (int) part no matter how many times I tried.

i tried using quadgk function as searched on the net, but the same message appears.

I wish to obtain numeric integration answer, so I didn't use syms x.

Really appreciate your help !

e=zeros(200); %store the calculated value in e array 
double x;
for i=1:1:200       
for j=1:1:200
          x=i-100;
          y=j-100;
          rho=sqrt(x^2+y^2); %To generate rho values to sub into e equation
e(i,j)=double(int(cos(x)^0.5*sin(2*x)*((exp(1)^(-(9/4)*(sin(x)/sin(1.125))^2))*(besselj(1,3*(sin(x)/sin(1.125)))))*(besselj(1,2*3.142*rho*sin(x))),0,1.125));
       end
  end

% %

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Answer 1

Walter Roberson 2013-1-12

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https://ww2.mathworks.cn/matlabcentral/answers/58604-undefined-function-or-method-int-for-input-arguments-of-type-double#answer_70893

在 MATLAB Online 中打开

You appear to be attempting to do numeric integration. int() is only for symbolic integration. There are a number of numeric integration routines such as quadgk()

Side note:

double x;

would be the same thing as

double('x');

which would convert the letter 'x' to double precision and then throw away the result.

MATLAB does not use declarations of type. Dataypes are determined by assignment.