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MathGroup Archive 1998

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Re: Unexpected results

  • To: mathgroup at smc.vnet.net
  • Subject: [mg14274] Re: Unexpected results
  • From: tdelling at ews.uiuc.edu (Tim Dellinger)
  • Date: Mon, 12 Oct 1998 13:51:53 -0400
  • Organization: University of Illinois at Urbana-Champaign
  • References: <6vf4vc$dg9@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Daniel Zepeda <dzepeda at ringer.cs.utsa.edu> writes:

>Plot[10^Log[x], {x, 0,10}] 

>plot what I expect? I expect it to plot y=x, but it doesn't, it plots an
>what looks like an exponential curve. 

This is the stupidest thing that Mathematica does.  It's really
downright user-unfriendly.  Log[x] gives you the natural log of x.  Not
what you'd expect, eh?  

One of the great things about Mathematica is that you can play with it
to see what's going on.  Try Log[100.] or N[ Log[100] ].  You'd expect
to get the answer 2.  But you don't get it!  So therein lies your
problem.

Another great thing about Mathematica is online documentation.  Try  ?
Log
and see what you get.  It will explain that Log[x] really means the
natural log of x, and if you want the base 10 log, try Log[10,x].

I think that base 10 should be the default instead of base e, as it is
conventional to use log[x] and ln[x] as notation.  If you want to
change the base to e, you should either have to do that manually, or
have a  separate function Ln[x].  The main reason I think so is that it
helps  people who are new to Mathematica, and it would increase
readability. Or perhaps Log[] should require two arguments, with no
defaults.

That's one of my major peeves with Mathematica.


--
__
Tim Dellinger                                www.ews.uiuc.edu/~tdelling
tdelling at uiuc.edu


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