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Re: Exponential of very small numbers [message #84280 is a reply to message #84279]

Wed, 08 May 2013 09:42

wlandsman
Messages: 743
Registered: June 2000

Senior Member

For x very close to zero I would use the approximation
exp(x) = x

or you could display all the digits (and use double precision)

IDL> print,EXP(1.6671699d-013)-1
1.6675550e-13
IDL> print,EXP(1.6671699d-013),f='(f24.18)'
1.000000000000166755

--Wayne

On Wednesday, May 8, 2013 12:14:19 PM UTC-4, Jacopo D wrote:
> Hello, first post ;)
>
> i need to integrate the planck distribution on IDL, but i have a problem with the exponential.
>
> The error is:
>
> EXP(1.6671699e-013)=1
>
>
>
> What can i do to avoid this problem? Even if it's an exponent very close to zero, it's important for my code.
>
> Thanks!

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		Re: Exponential of very small numbers By: Jacopo D on Wed, 08 May 2013 10:40
		Re: Exponential of very small numbers By: wlandsman on Wed, 08 May 2013 09:42

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