Exponential of very large number

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Teshome Kumsa
Teshome Kumsa 2021-8-28
评论： Steven Lord 2021-8-28
Hello all! I was trying to calculate exponental of some vectors. Actually my vector has very big entries(each entries are Stresses accumulated during earquakes. That is why they are very big).
For example
exp([-235628865.417257 29372700213.5032]/10.^5)
It returns ans=
0 Inf
I need a comment on it.
  1 个评论
Matt J
Matt J 2021-8-28
It wouldn't make sense to take exp() to any greater precision unless you are going to take the log of it later.

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回答（1 个）

Chunru
Chunru 2021-8-28
编辑：Chunru 2021-8-28
Ran in:
Those number are beyond the scope of double numbers. You can try vpa. Alternatively, keep track of the mantisa and exponent yourself as follows:
a=log10(exp(1))*([-235628865.417257 29372700213.5032]/10.^5);
aint = ceil(a);
afrac = a -aint;
xm = 10.^afrac;
xe = aint;
xstr = xm(:)+" x 10 ^ "+xe(:)
xstr = 2×1 string array
"0.47516 x 10 ^ -1023" "0.1038 x 10 ^ 127565"
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显示 1更早的评论
Chunru
Chunru 2021-8-28
The code uses your edited numbers now.
Steven Lord
Steven Lord 2021-8-28
What are you hoping to do with those answers? Are you planning on dividing them by exp(x) for some other value of large magnitude?

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