使用mupadmex时出错，符号/符号错误(求定积分) [英] Error using mupadmex, Error in sym/symsum (Evaluate a definite integral)

问题描述

我正在尝试使用以下代码评估定积分:

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)

但是它给出了以下错误:

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)

但是，当我评估不带某些功能的积分时:

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) 

我得到的答案是Inf.有什么主意吗?

I get an answer which is Inf. Any idea?

推荐答案

我找到了解决方案.它包括使用gamma(k + n-m + 1)来计算(k + n-m)!，因为执行符号变量的阶乘时会出现错误.

I found the solution. it consists in using gamma(k+n-m+1) to compute (k+n-m)!, since there is a bug when performing the factorial of a symbolic variables.

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