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Re: Extension of MatrixExp



> Dear MathGroup users,
>
> MatrixExp is not able to give me a nice answer in the following very
> easy case:
>
> In[1] = m = {{2,0,0},{0,3,0},{0,0,4}} ; (* A diagonal matrix *)
>
> In[2] = MatrixExp[t*m]
>
> I define my own function
>
> The result is ok, but perhaps somebody have a best (more compact)
> solution...
>
> Thank you for your answers.
>
> Fred lang

Try using ToRadicals:

In[1]:= m = {{2,0,0},{0,3,0},{0,0,4}} ;

In[2]:= MatrixExp[t m] //ToRadicals

           2 t              3 t              4 t Out[2]= {{E   , 0, 0},
{0, E   , 0}, {0, 0, E   }}

The fact that you need to do this is an oversight in Version 3.0.  This
will almost certainly be changed for the next release of Mathematica.

Dave Withoff
Wolfram Research



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