Error using mupadmex, Error in sym/symsum (Evaluate a definite integral)

I am trying to evaluate a definite integral using the following code :

 m=4;
 t=4;
 n=5;
 P=10;
 reset(symengine)
 syms x;
 syms k;
mean=int(log(1+P*x/t)*symsum( factorial(k)*x^(n-m)*exp(-x)/factorial(k+n m)*feval(symengine,'laguerreL',n-m,k,x)*feval(symengine,'laguerreL',n-m,k,x),k,[0,m-1]) ,x,0,inf)

But it gives the following error:

      Error using mupadmex
      Error in MuPAD command: The number of arguments is incorrect. [has]
      Evaluating: sum

      Error in sym/symsum (line 114)
      rSym = mupadmex('symobj::map',fsym.s,'symobj::symsum',x.s,a.s,b.s);

      Error in Untitled2 (line 32)
      mean=int(log(1+P*x/t)*symsum( factorial(k)*x^(n-m)*exp(-x)/factorial(k+n-m)*feval(symengine,'laguerreL',n-m,k,x)*feval(symengine,'laguerreL',n-m,k,x),k,[0,m-1]) ,x,0,inf)

However, when I evaluate the integral without some functions:

mean=int(log(1+P*x/t)*symsum( feval(symengine,'laguerreL',n-m,k,x)*feval(symengine,'laguerreL',n-m,k,x),k,[0,m-1]) ,x,0,inf)

I get an answer which is `Inf`. Any idea?

Answer 1

[Walter Roberson]

It appears to me that you tried to use the syntax symsum(expr,var,a,b) but instead you used the syntax symsum(expr,var,[a,b])

[dina guermaz]

I tried with the first syntax and still have the same problem.

[Walter Roberson]

As a side point: I notice you have

feval(symengine,'laguerreL',n-m,k,x) * feval(symengine,'laguerreL',n-m,k,x)

Is there a reason why you did not use

feval(symengine,'laguerreL',n-m,k,x)^2

?

[dina guermaz]

No, there is no specific reason. But still not working even if I use (..)^2.

[Walter Roberson]

I do not have the toolbox to test with, but my expectation would be that this should work:

mean = int(log(1+P*x/t) * symsum( factorial(k) * x^(n-m) * exp(-x) / factorial(k+n m) * feval(symengine,'laguerreL',n-m,k,x)^2,k,0,m-1), x, 0, inf)

Except of course I would never use "mean" as the output variable name since it is the name of a MATLAB function.

You could try breaking up the parts just in case it is complaining about something inside the symsum:

LL = feval(symengine,'laguerreL',n-m,k,x)^2;
to_sum = factorial(k) * x^(n-m) * exp(-x) / factorial(k+n m) * LL;
ss = symsum(to_sum, k, 0, m-1);
to_int = log(1+P*x/t) * ss;
result = int(to_int, x, 0, inf);

[dina guermaz]

Using your last code (and the first one), Matlab still giving an error:

Error using mupadmex
Error in MuPAD command: The number of arguments is incorrect. [has]
Evaluating: sum
Error in sym/symsum (line 114)
rSym = mupadmex('symobj::map',fsym.s,'symobj::symsum',x.s,a.s,b.s);
Error in Untitled11 (line 16)
ss = symsum(to_sum, k, 0, m-1);

By the way there is a - missed in your code

[Walter Roberson]

I would need the toolbox to do more testing, sorry.

One thing I note is that the "[has]" suggests to me that inside symsum() a MuPAD has() call is being attempted and is failing.

Did you happen to create your own MuPad procedures? Look for .mu files on your path. http://www.mathworks.com/help/symbolic/use-your-own-mupad-procedures.html . Though the possibility of having overridden has() is more something I would associate with a MuPAD library that has somehow automatically been executed. I have not examined how MuPAD user libraries are created.

Maybe try the instructions at http://www.mathworks.com/help/symbolic/source-code-of-the-mupad-library-functions.html to display 'symsum' and 'has'

Answer 2

[Dharini V]

Error using mupadmex
Error in MuPAD command: The dimensions do not match.
[(Dom::Matrix(Dom::ExpressionField()))::_mult2]

Error in sym/privBinaryOp (line 1693)
            Csym = mupadmex(op,args{1}.s, args{2}.s, varargin{:});

Error in sym/mtimes (line 179)
        X = privBinaryOp(A, B, 'symobj::mtimes');

Error in first (line 78)
    E_phi=1j*beta*exp(-1j*beta*r)*cos(theta)*(Py*cos(phi)-Px*sin(phi))/(2*pi*r);