Triplequad function with symbolic variables

Hi Dear Matlab users

My problem is I wrote a function just below.

function out = ahmet(r,s,zeta)

syms z1

out=2*r.^2*s.^4*zeta*z1;

end

Then I called this function to be used for

k=triplequad('ahmet',-1,1,-1,1,-1,1)

It gives me errors telling that ''Inputs must be floats, namely single or double.''

If I omit z1 variable which is symbolic then it evaluates the quadrature but I want z1 stay and not calculated in the equation. Is it possible for quadrature ?

It is possible for int() command using symbolic variables. But I have to bring together both quadrature and symbolic variables ?

Thank you

Answer 1

[Walter Roberson]

syms r s zeta
k = int( int( int( ahmet(r, s, zeta), r, -1, 1), s, -1, 1), zeta, -1, 1);

Note that the result (if it can be analytically found) will likely have z1 as a free variable.

Caution: if you replace the limits of integration for zeta with "a" and "b", the integral works out as (4/15)*z1*(b^2-a^2) . And when abs(a) = abs(b) as is the case for -1 to +1, the solution is going to be identically 0 for all values of z1.

[Kazim]

Thank you Mr. Walter Roberson I tried your solution but my function is more complicated and when I used int it says explicit integral can not be found. For this reason I decided to use quadrature.

I have found quadl below. It says additional arguments p1,p2 to be passed directly to function. Could we use it ?

quadl(fun,a,b,tol,trace,p1,p2,...) provides for additional arguments p1,p2,... to be passed directly to function fun, fun(x,p1,p2,...). Pass empty matrices for tol or trace to use the default values

For example; quadl('ahmet',-1,1,[],[],s,zeta,z1)

function out = ahmet(r,s,zeta,z1)

out=2*r.^2*s.^4*zeta*z1;

end

function out = ahmet(r,s,zeta,z1)----> Here I have a problem for input arguments sequence ? Because quadl uses ahmets r input for -1 and 1 then tol and trace comes then I think if I have to empty two matrix for tol and trace parts in ahmet function input arguments like ahmet(r,[],[],s,zeta,z1) ?

Thank you