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MathGroup Archive 2003

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Re: Part 2 of a recent post on Plot and v 5

  • To: mathgroup at smc.vnet.net
  • Subject: [mg44600] Re: Part 2 of a recent post on Plot and v 5
  • From: "Peltio" <peltio at twilight.zone>
  • Date: Mon, 17 Nov 2003 03:38:34 -0500 (EST)
  • References: <boigjd$oih$1@smc.vnet.net>
  • Reply-to: "Peltio" <peltioNOSP at Miname.com.invalid>
  • Sender: owner-wri-mathgroup at wolfram.com

"Bill Rowe" wrote

>> My opinion is that an EXPLICITLY given range in any of the graphics
>> commands should not be overridden, under any circumstances.
>> Is there anyone who agrees with me?
>Yes, I would agree with you. But, in Mathematica, explicity giving
>a plot range means adding a PlotRange->{values} directive.

But when a user ask Mathematica to evaluate

    Plot[f[x], {x,a,b}]

is because he or she wants to see how the function f[x] behaves on _that_
interval. Be it 'interesting' or dead flat. I do not have access to version
5, but I gather that the behavior is that the output shows the function over
a subrange (-1<x<1).

Since the user is already supplying an explicit range, why should he/she do
that twice? I feel that a computer program should not take the initiative
over the user, unless an Automatic mode is set on purpose. In my opinion it
would be advisable to have

    >SetOptions[Plot, PlotRange->{All, Automatic}]

as the default behavior (the Automatic setting on the y-range is advisable
since the user is not supplying direct information on that range), because
it is less confusing with respect to the expected behavior.
So now the problem is what is meant by 'expected', as this could be a
subjective issue. In the case of a computer program it should be to follow
the user instructions (literally, I'd say) [1].
Plot[f[x],{x,a,b}] should mean "show me the plot of the function f[x] when x
varies between a and b", should it not?

Agreed, the problem is easily solvable by setting a specific option in one's
Init file, but I feel it should be the other way round.
The 'stupid' behavior has the advantage to be predictable.
The 'smart' behaviour is not, especially when the average user does not know
what kind of algorithm is behind it.

My two cents, of course.
Nothing more.

cheers,
Peltio
invalid address in reply-to, crafty demunging required to mail me

[1] Anyone recall the behavior of smart elevators in Douglas Adams'
"Hitchhiker's Guide to the Galaxy"?
    "I go up," said the elevator, "or down."
    "Good," said Zaphod, "We're going up."
    "Or down," the elevator reminded him.
    "Yeah, OK, up please."
    There was a moment of silence.
    "Down's very nice," suggested the elevator hopefully.
: ]
(incidentally, the elevator was right in not wanting to go up : ))) )


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