Exponential of big numbers

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Arianna Menardi
Arianna Menardi 2020-4-27
回答： Arianna Menardi 2020-5-1
Dear Experts,
I need to compute the following formula: M= expm(atilde*T).
However, the atilde*t results in a matrix of big numbers and when I do the expm matlab gives back a matrix of NaN as it is not able to handle them (from my understanding). I tried with vpi from this toolbox (https://www.mathworks.com/matlabcentral/fileexchange/22725-variable-precision-integer-arithmetic) by doing M=expm(vpi(atilde*T)) but it doen't work as it gives me back the error that expm requires input of type double or single and instead the type is VPI.
Does anyone has a suggestion on how to deal with this problem?
Thank you so much!
Arianna
  1 个评论
Steven Lord
Steven Lord 2020-4-27
How big are your "big numbers" in terms of magnitude?
Can you show a representative (small in terms of number of elements) matrix atilde*T?

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回答（2 个）

David Hill
David Hill 2020-4-27
Try:
M=expm(vpa(atilde*T));
Arianna Menardi
Arianna Menardi 2020-5-1
Dear all, thank you for your suggestions! I actually found out that I needed to stabilize my matrix (dividing it by its max eigenvalue). Scaling it enabled my matlab to compute the code.
All the best

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