'I get error saying Input function must return 'double' or 'single' values. Found 'sym'.' because max is defined in symbolic variable, how to overcome this issue??

syms x y b

fun = @(x,y)x.^2;

subplot(2,1,1)

ezsurf(fun)

xmin = 0;

xmax = 4;

ymin =0;

ymax = @(x) b.*sqrt(x);

Q = integral2(fun,xmin,xmax,ymin,ymax)

Answer 1

[Steven Lord]

Your ymax function returns a sym result. If you specify the limits as function handles in your call to integral2 those function handles must return a numeric result, not a symbolic result.

If you want to integrate with a symbolic limit, work solely with symbolic variables and call the int function twice instead of calling integral2.

If you want to be able to specify b when you call integral2 rather than when you define the ymax function:

ymax = @(x, b) b.*sqrt(x);

Now when you call integral2 (I'm assuming you've defined fun, xmin, xmax, and ymin before this call) specify b:

% Use b = 1
Q = integral2(fun, xmin, xmax, ymin, @(x) ymax(x, 1));

% Use b = x.^2
Q = integral2(fun, xmin, xmax, ymin, @(x) ymax(x, x.^2));

[madhan ravi]

hi @steven thank you for answering I tried. what you told:

>> syms x y b

fun = @(x,y)x.^2;

subplot(2,1,1)

ezsurf(fun)

xmin = 0;

xmax = 4;

ymin =0;

ymax = @(x,b) b.*sqrt(x);
b=1
Q = integral2(fun,xmin,xmax,ymin,ymax)

b =

       1

Not enough input arguments.

Error in @(x,b)b.*sqrt(x)

Error in integral2Calc>integral2t/tensor (line 190)
        top = YMAX(x);

Error in integral2Calc>integral2t (line 55)
[Qsub,esub] = tensor(thetaL,thetaR,phiB,phiT);

Error in integral2Calc (line 9)
    [q,errbnd] =
    integral2t(fun,xmin,xmax,ymin,ymax,optionstruct);

Error in integral2 (line 106)
    Q =
    integral2Calc(fun,xmin,xmax,yminfun,ymaxfun,opstruct); 
>>

[Steven Lord]

The fifth input to your integral2 call and the fifth input to my integral2 call are different. In your call, you're passing an anonymous function that requires two inputs into integral2. In mine, I pass an anonymous function that requires only one input into integral2.

[madhan ravi]

Still the same.

[Steven Lord]

 ...
  ymax = @(x,b) b.*sqrt(x);
  b=1
  Q = integral2(fun,xmin,xmax,ymin,@(x) ymax(x, b))

[madhan ravi]

It works @steven thank you but is it not possible to keep the limit as symbolic variable that’s the main motive here?

[Steven Lord]

Not with integral2, no. If you want to integrate with a symbolic limit, work solely with symbolic variables and call the int function twice instead of calling integral2.

[madhan ravi]

Thank you so much for sparring your time and I highly appreciate your efforts ?->(Indian way of thanking)