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log base 10

asked 2011-12-01 05:46:54 -0500

Jason gravatar image

Is there a built-in way to use a log with base other than e? The log documentation doesn't show any example (I thought log(10,x) was what I wanted for a while but it's actually different than what one might expect).

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answered 2011-12-01 06:07:22 -0500

kcrisman gravatar image

This is in log?:

   EXAMPLES:

      sage: log(e^2)
      2
      sage: log(1024, 2); RDF(log(1024, 2))
      10
      10.0

So log(x,10) should be what you're looking for...

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Thanks, I wasn't aware that log_b(x) was equivalent to log(x)/log(b). Might be good to add that to the docs. (I got hung up because I saw log(10)/log(2) in the log? documentation and assumed it meant that log(x,y) was something that didn't help me, because it didn't say "To use the log in base b, do this")

Jason gravatar imageJason ( 2011-12-01 06:23:51 -0500 )edit

Well, the very first line of `log?` is "Return the logarithm of x to the given base." See http://www.sagemath.org/doc/reference/sage/functions/log.html#sage.functions.log.log. But if you think we should be a little more explicit, let us know and we could open a ticket...

kcrisman gravatar imagekcrisman ( 2011-12-01 08:53:05 -0500 )edit

If you could make this change it would be great: "EXAMPLES: sage: log(e^2)" : To something like: EXAMPLES: To change the base of the logarithm, add a second parameter. sage: log(1000,10): 3 Small change but helpful!

Jason gravatar imageJason ( 2011-12-01 09:16:40 -0500 )edit
kcrisman gravatar imagekcrisman ( 2011-12-03 03:46:20 -0500 )edit

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Asked: 2011-12-01 05:46:54 -0500

Seen: 5,891 times

Last updated: Dec 01 '11