Error Undefined x!

In my script, I call a function value to input values and put the input in another function integrnfn:

[A,x1,x2]=value;

y=integrfn(A,x1,x2);

fprintf('The value of the integral is %.3f', integrfn(A,x1,x2))

function [A,x1,x2]=value

A=input('Please enter a positive value: ');

x1=input('Please enter another positive value: ');

x2=input('Please enter a positive value that is greater than the previous one: ');

end 

function y=integrfn(A,x1,x2)

y=int(A*exp(-x^2)*cos(2*x)/(1+x^2),x,x1,x2);

end

However, when I run it, it says:

Undefined function or variable 'x'.

Error in script >integrfn (line 15)
y=int(A*exp(-x^2)*cos(2*x)/(1+x^2),x,x1,x2);

Error in the script (line 5)
y=integrfn(A,x1,x2);

Can someone tell me the problem?

Thank you!!

Answer 1

[Star Strider]

The int function is part of the Symbolic Math Toolbox. The most appropriate function is integral, with the integrand as an anonymous function:

y = integral(@(x) A*exp(-x.^2).*cos(2*x)./(1+x.^2),x1,x2);

[Zhuoying Lin]

But it turns out that regardless of the input the output value is always o. Why?

[Star Strider]

That is not the result I get:

A = 5;
x1 = 1;
x2 = 10;
y=integral(@(x) A*exp(-x.^2).*cos(2*x)./(1+x.^2),x1,x2)

y =
  -188.9829e-003

I do not see any errors in your code that would lead that a result always being 0.

[Zhuoying Lin]

The result is right only if I type the number and equation directly, yet if I run the whole script the result is always 0.

[Star Strider]

This code works for me:

function [A,x1,x2]=value

A=input('Please enter a positive value: ')

x1=input('Please enter another positive value: ')

x2=input('Please enter a positive value that is greater than the previous one: ')

end 

function y=integrfn(A,x1,x2)

y = integral(@(x) A*exp(-x.^2).*cos(2*x)./(1+x.^2),x1,x2);

end

[A,x1,x2]=value

y=integrfn(A,x1,x2)

fprintf('The value of the integral is %.3f', integrfn(A,x1,x2))

When I run it:

Please enter a positive value: 10

A =

      10.0000e+000

Please enter another positive value: 1

x1 =

       1.0000e+000

Please enter a positive value that is greater than the previous one: 5

x2 =

       5.0000e+000

A =

      10.0000e+000

x1 =

       1.0000e+000

x2 =

       5.0000e+000

y =

    -377.9658e-003

The value of the integral is -0.378

[Zhuoying Lin]

I figure out why now. Thank you!

[Star Strider]

My pleasure!