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Groups > comp.soft-sys.math.mathematica > #1679
| From | David Bailey <dave@removedbailey.co.uk> |
|---|---|
| Newsgroups | comp.soft-sys.math.mathematica |
| Subject | Re: Coloring curves: not as simple as it sounds.. |
| Date | 2011-04-14 11:08 +0000 |
| Organization | Steven M. Christensen and Associates, Inc and MathTensor, Inc. |
| Message-ID | <io6kj1$ffc$1@smc.vnet.net> (permalink) |
| References | <io6d17$dpl$1@smc.vnet.net> |
On 14/04/2011 09:59, Jean-Michel Di Nicola wrote:
> All,
>
> I have a question that looks fairly trivial, but I cannot solve it....
> Please help!
>
> Thanks, JM
>
> Here is a simplified toy example.
> When I type
> Plot[{a x /. {a -> 1}, a x^2 /. {a -> 1}, a x^3 /. {a -> 1}}, {x, 0,
> 2}, PlotStyle -> {Red, Green, Blue}]
> I get 3 curves with different colors.
>
> Well, when I type
> Plot[{a x, a x^2, a x^3} /. {a -> 1}, {x, 0, 2},
> PlotStyle -> {Red, Green, Blue}]
> I get 3 curves but they are all blue, WHY?
>
> However, when I evaluate {a x /. {a -> 1}, a x^2 /. {a -> 1}, a x^3 /.
> {a -> 1} and {a x, a x^2, a x^3} /. {a -> 1}, they both give the same
> result....{x, x^2, x^3}.
>
> Thank you for your help!!!
>
Plot looks at its argument to see if it is a list before it starts to
evaluate it at particular points - so if the list structure is only
apparent after evaluation, it doesn't work as required. This fixes it:
Plot[Evaluate[{a x, a x^2, a x^3} /. {a -> 1}], {x, 0, 2},
PlotStyle -> {Red, Green, Blue}]
The fact that it plotted at all, surprised me, so I did a couple of
experiments:
This plots two curves
Plot[If[x<-2,x^2,{x^2,x^3}],{x,1,10}]
But if the expression to be plotted only returns a list for part of the
range, only one curve results!
Plot[If[x<2,x^2,{x^2,x^3}],{x,1,10}]
David Bailey
http://www.dbaileyconsultancy.co.uk
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Coloring curves: not as simple as it sounds.. Jean-Michel Di Nicola <jeanmichel.dinicola@gmail.com> - 2011-04-14 08:59 +0000
Re: Coloring curves: not as simple as it sounds.. David Bailey <dave@removedbailey.co.uk> - 2011-04-14 11:08 +0000
Re: Coloring curves: not as simple as it sounds.. Jean-Michel Di Nicola <jeanmichel.dinicola@gmail.com> - 2011-04-15 07:55 +0000
Re: Coloring curves: not as simple as it sounds.. Chris Rodgers <see-rodgers-org-uk-for-contact-details@invalid.gg> - 2011-04-14 11:08 +0000
Re: Coloring curves: not as simple as it sounds.. Peter Pein <petsie@dordos.net> - 2011-04-15 07:55 +0000
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