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Re: What's going on here (Table-generated lists)?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg98104] Re: What's going on here (Table-generated lists)?
  • From: AES <siegman at stanford.edu>
  • Date: Mon, 30 Mar 2009 04:43:52 -0500 (EST)
  • Organization: Stanford University
  • References: <gqn8ua$p$1@smc.vnet.net>

In article <gqn8ua$p$1 at smc.vnet.net>,
 Bill Rowe <readnews at sbcglobal.net> wrote:

> >I still don't see why it doesn't make sense
> >for Plot to recognize a list as an actual list and plot each with a
> >different color.
> 
> Plot does this when the argument provided is a list, That is
> 
> Plot[{x,x^2},{x,0,1}]
> 
> will plot two curves in two different colors. 

But

     Plot[0.5{x,x^2}, {x,0,1}]

will not plot two curves in two different colors -- right? --
despite the fact that evaluating  0.5{x,x^2}  by itself 
displays as  {0.5 x, 0.5 x^2} );  and

     Plot[{0.5x, 0.5x^2}, {x, 0, 1}]

does plot two curves in two different colors

> What answer are you looking for here?

In my case (I'm not the OP), not an explanation of why this happens 
(I've come to sort of understand this); but as purely curiosity 
questions (since this behavior of Plot comes up time after time):

1)  Is having this weird and confusing behavior in the Plot[] command 
somehow necessary, unavoidable, for reasons deep in the fundamental 
structure of Mathematica? -- or is this merely a bad design choice made 
long ago, that one would wish could now be extirpated (but probably 
can't be)?

2)  Does Wolfram have any understanding of how much the string of 
endless "gotchas" like this damage the usability of Mathematica for 
ordinary users (as contrasted to full time professional programmers)?

3)  Should maybe evaluating  0.5{x,x^2}  by itself display as  

   { {0.5 x, 0.5 x^2} }

since that's what it really is?  (Or should Plot[] maybe strip off the 
outer { }'s if given this as the function to be plotted?)


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