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matlabeval

Evaluating a function defined symbolically with subs

eta0=-0.1806 - 0.1043i; 

syms lu
syms n

Gi(lu) = -(airy(2,lu)*int(airy(n),100,lu)-airy(lu)*int(airy(2,n),eta0,lu));

I am unable to evaluate a function defined like that e.g. Gi(2). How can this be done? I tried subs(Gi,lu,2) and eval(subs(Gi,lu,2)) but they don't work

Solution

  • Instead of messing around with symbolic toolbox, to evaluate the function itself, you can use anonymous function. 

    eta0=-0.1806 - 0.1043i; 

Gi = @(lu) -( airy(2,lu)*integral(@airy,100,lu)- ....
    airy(lu)*integral(@(x) airy(2,x),eta0,lu) );

    Symbolic function takes symbolic numbers, Anonymous function takes numeric numbers. Perhaps this is an easier way to perform a simple function. 

    >> Gi(2)

ans =

   0.1727 + 0.0019i