exp(A) gives zero in the first argument

Question

Antonios Nasioulas 2019-10-19

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链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/486290-exp-a-gives-zero-in-the-first-argument

评论： Star Strider 2019-10-19

采纳的回答： Star Strider

在 MATLAB Online 中打开

When I compute for example

exp([71 307])

on matlab (on my laptop version) I get

ans =
  1.0e+133 *
    0.0000    2.1301

Which seems pretty unreasonable to me as 71 is not that big and of course not bigger than 307.

Also if I put the same computation on octave online I get

ans =
    6.8377e+30   2.1301e+133    

which makes tottaly sense.

Do you know what is going wrong?

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Answer 1

Star Strider 2019-10-19

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/486290-exp-a-gives-zero-in-the-first-argument#answer_397175

在 MATLAB Online 中打开

Try this:

format longE
exp([71  307])

producing:

ans =
     6.837671229762744e+30    2.130129192828224e+133

See the documentation on format for more information.

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Antonios Nasioulas 2019-10-19

Yes, this works.

But is there a bug on my version or what happens and I get this odd result?

Star Strider 2019-10-19

There is no bug. The default format is short. You can change it in the Preferences to something else, or change it specifically for one calculation or a set of calculations as I did here, then (if you want to), change it back to a previous definition. The chosen format will be whatever you chose for it when you start MATLAB, and if you change it, the change will remain until you change it to something else. See the documentation I linked to for details.

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