Re: ListPlotFit
- To: mathgroup at smc.vnet.net
- Subject: [mg17231] Re: ListPlotFit
- From: Allan Hayes <hay at haystack.demon.co.uk>
- Date: Fri, 30 Apr 1999 02:34:30 -0400
- References: <7fp3um$31l@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Maarten
Thanks for the information about Roman Maeder's approach.
I would like to add localization of the variable default in
> ListPlotFit[l_, start_:1, stop_:default] :=
> Module[{lp, fie, fiep},
> lp = ListPlot[l, DisplayFunction -> Identity, PlotStyle ->
> PointSize[0.015], PlotRange -> All];
> If[stop===default, stop = Length[l]];
> fie = Fit[l[[Table[j, {j, start, stop}]]], {1, x}, x];
> fiep = Plot[fie, {x, 1, Length[l]}, DisplayFunction -> Identity];
> Show[lp, fiep, DisplayFunction -> $DisplayFunction]]
>
For extreme example of what might happen without this use the definition
with the assignment
default := (Print["Fail"];Throw)
either before or after defining ListPlotFit.
One way out is to use an outer Module:
Module[{default},
ListPlotFit[l_, start_:1, stop_:default] :=
Module[{lp, fie, fiep},
lp = ListPlot[l, DisplayFunction -> Identity, PlotStyle ->
PointSize[0.015], PlotRange -> All];
If[stop===default, stop = Length[l]];
fie = Fit[l[[Table[j, {j, start, stop}]]], {1, x}, x];
fiep = Plot[fie, {x, 1, Length[l]}, DisplayFunction -> Identity];
Show[lp, fiep, DisplayFunction -> $DisplayFunction]]
]
Or, use one Module round the lot.
A less secure way is to use the string "default" instead of the symbol
default (this can be affected by replacement - "default" -> Throw.
But then we can make a mess of anything with injudicious use of replacement.
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565
<Maarten.vanderBurgt at icos.be> wrote in message
news:7fp3um$31l at smc.vnet.net...
> Alan,
>
> Thanks for your help.
> Bob Hanlon gave me a simalar answer.
> Another approach I found in R. Maeder's book:
>
> ListPlotFit[l_, start_:1, stop_:default] :=
> Module[{lp, fie, fiep},
> lp = ListPlot[l, DisplayFunction -> Identity, PlotStyle ->
> PointSize[0.015], PlotRange -> All];
> If[stop===default, stop = Length[l]];
> fie = Fit[l[[Table[j, {j, start, stop}]]], {1, x}, x];
> fiep = Plot[fie, {x, 1, Length[l]}, DisplayFunction -> Identity];
> Show[lp, fiep, DisplayFunction -> $DisplayFunction]]
>
> Maarten
>
>
>
>
>
> "Allan Hayes" <hay at haystack.demon.co.uk> on 19-04-99 05:53:52 PM
>
> cc:
>
> Subject: [mg17231] [mg17231] Re: ListPlotFit
>
>
>
>
> Marrten,
>
> ListPlotFit[l_, start_:1, stop_] :=
> Module[
> {lp, fie, fiep},
> lp = ListPlot[l, DisplayFunction -> Identity, PlotStyle ->
> PointSize[0.015], PlotRange -> All];
> fie = Fit[l[[Table[j, {j, start, stop}]]], {1, x}, x];
> fiep = Plot[fie, {x, 1, Length[l]}, DisplayFunction -> Identity];
> Show[lp, fiep, DisplayFunction -> $DisplayFunction]
> ]
>
> ListPlotFit[l_, start_:1]:=
> ListPlotFit[l, start, Length[l]]
>
> Allan
>
> ---------------------
> Allan Hayes
> Mathematica Training and Consulting
> Leicester UK
> www.haystack.demon.co.uk
> hay at haystack.demon.co.uk
> Voice: +44 (0)116 271 4198
> Fax: +44 (0)870 164 0565
>
>
> <Maarten.vanderBurgt at icos.be> wrote in message
> news:7fbnsj$957 at smc.vnet.net...
> > Hello,
> >
> >
> > With the function ListPlotFit below I combine ListPlot with Fit and Plot
> in
> > order to show the data from list l together with the straight line
fitted
> > through a part of the data points from list l. The list l is of form
> > {{x1,y1},{x2,y2}, ...}.
> >
> > The part of the data points I want to fit a line through is determined
by
> > start and stop. The default value for the optional argument stop is 10.
> > This is not really what I want: I want the default value for stop to be
> > stop = Length[l]. How can I achieve this?
> >
> > I tried ListPlotFit[l_, start_:1, stop_:Hold[Lenght[l]] :=
Module[{},stop
> =
> > ReleaseHold[stop];...], but this did not work (I get an error: "Hold is
> > Protected..."). I think I need Hold or something of the sort otherwise
> > Lenght[l] gets evaluated to 1 immediately.
> >
> > I guess I can phrase my question more general: how do I define a
function
> F
> > with an optional argument v which has as default value a function g of a
> > non-optional argument u (i.e. F[u_, v_:g[u]])?
> >
> >
> > In[1]:= ListPlotFit[l_, start_:1, stop_:10] :=
> > Module[
> > {lp, fie, fiep},
> > lp = ListPlot[l, DisplayFunction -> Identity, PlotStyle ->
> > PointSize[0.015], PlotRange -> All];
> > fie = Fit[l[[Table[j, {j, start, stop}]]], {1, x}, x];
> > fiep = Plot[fie, {x, 1, Length[l]}, DisplayFunction -> Identity];
> > Show[lp, fiep, DisplayFunction -> $DisplayFunction]
> > ]
> >
> > In[2]:= dat= Table[{i,3*i^2+5+2*(Random[]-0.5)},{i,1,15}];
> > In[3]:= ListPlotFit[dat, 2, 12];
> >
> >
> > Any help is greatly appreciated
> > thanks
> >
> > Maarten
> >
> >
> > _______________________________________________________________
> >
> > Maarten van der Burgt
> > R&D Department
> >
> > ICOS Vision Systems
> > Esperantolaan 9
> > B-3001 Leuven, Belgium
> > tel. + 32 16 398220; direct + 32 16 398316; fax. + 32 16 400067
> > e-mail: maarten.vanderburgt at icos.be
> > _______________________________________________________________
> >
> >
> >
> >
> >
>
>
>
>
>
>