# [R] Searching for antilog function

Heather J. Branton hjb at pdq.com
Wed Nov 24 20:38:19 CET 2004

```Thank you so much for each of your responses. But to make sure I am
clear (in my own mind), is this correct?

If  x = 2^y
Then  y = log2(x)

Thanks again. I know this is basic.

...heather

Duncan Murdoch wrote:

>On Wed, 24 Nov 2004 12:26:46 -0500, "Heather J. Branton" <hjb at pdq.com>
>wrote :
>
>
>
>>Dear R-users,
>>
>>I have a basic question about how to determine the antilog of a variable.
>>
>>Say I have some number, x, which is a factor of 2 such that x = 2^y. I
>>want to figure out what y is, i.e. I am looking for the antilog base 2 of x.
>>
>>I have found log2 in the Reference Manual. But I am struggling how to
>>get the antilog of that.
>>
>>
>
>You seem to be confusing log with antilog, but log2(x) and 2^y are
>inverses of each other, i.e.
>
>log2(2^y) equals y
>
>and
>
>2^log2(x) equals x
>
>(up to rounding error, of course).
>
>Duncan Murdoch
>
>
>
>

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```