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Re: newbie: can't Manipulate ListPlot of recurrence
*To*: mathgroup at smc.vnet.net
*Subject*: [mg96818] Re: newbie: can't Manipulate ListPlot of recurrence
*From*: Albert Retey <awnl at gmx-topmail.de>
*Date*: Wed, 25 Feb 2009 04:07:14 -0500 (EST)
*References*: <go0j40$n0f$1@smc.vnet.net>
Tom Roche wrote:
> summary: I'm trying to Manipulate the logistic map. I can ListPlot it,
> but when I try to Manipulate, the UI behaves weirdly.
>
> details:
>
> As advertised by the Subject:, I'm new to Mathematica (specifically
> 7.0.0 for Students for 32-bit Windows on XP Pro) so please excuse any
> lapses in terminology. I'd also appreciate pointers to specific docs
> rather than just an RTFM.
>
> I'm trying to model the logistic map y=a y (1-y):
>
> http://en.wikipedia.org/wiki/Logistic_map
> http://mathworld.wolfram.com/LogisticMap.html
> http://www.phy.duke.edu/~palmer/notebooks/LogisticMap.nb
>
> To start with I just tried to plot it, which works:
>
> Clear[a, y];
> a=3.5;
> y=0.4;
> ListPlot[Table[y=a y (1-y),{50}],Joined->True]
>
> I'd like to Manipulate a and y, but when I try to
>
> Clear[a, y];
> Manipulate[
> ListPlot[Table[y=a y (1-y),{50}],Joined->True], {{a, 3.5}, 0, 4},
> {{y, 0.4}, 0, 1}]
>
> I get weird behavior:
>
> 1 initially the y slider oscillates
>
> 2 initially the plot displays but flashes (apparently between two
> phases) until I click one of the sliders
>
> 3 the y slider will not move
>
> 4 the a slider can be dragged, but to no effect (i.e. the plot does
> not change)
all these come from the fact that you are asigning to y which is one of
the variables that you want to manipulate, which is almost never a good
idea...
> 5 there are no error messages
> What am I doing wrong? and how can I Manipulate this map?
I think this does what you want:
Clear[a, y];
Manipulate[
ListPlot[
Block[{x = y},
Table[x = a x (1 - x), {50}]
],
Joined -> True, PlotRange -> {0, 1}
],
{{a, 3.5}, 0, 4},
{{y, 0.4}, 0, 1}
]
hth,
albert
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