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Re: how to drop ContextPath when printing from a package?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg116412] Re: how to drop ContextPath when printing from a package?
  • From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
  • Date: Mon, 14 Feb 2011 04:26:25 -0500 (EST)

Hi Ted,

I see. Your function and problem differ are a  bit from what I assumed
originally.

The function you sent me actually works without problem. I think your
problem pops up if you pass a variable name that is local to another scoping
construction such as in (silly example):

Module[{x},
 fit1D[Range[10], RandomReal[{-0.3, 0.3}, 10] + 2 Range[10], a + b x, {a,
b}, x, "test string", "test file", True]
]

Passing a local variable is normally fine, but here you pass it as a symbol
(without value) in order to use its name and not its value. I'd say that's a
nono.

But let's try to get this to work as you intend. Since the user is free to
use any model and variable name replacement isn't as easy as before, but it
can be done using ToString and string pattern matching:
      x -> StringReplace[ToString[x], a_ ~~ "$" ~~ ___ -> a] which uses the
fact that all localized variables contain the "$-number" part.

As far as I can see, the following update of your code now works even for
localized variables (note that I changed the definition of f to include a
formal parameter):

fit1D[X_, Y_, model_, par_, x_, axesLabel_, fileName_, plotQ_] :=
  Module[{XY, xyFit, label, gr1, gr2, gr, f, myVar},(*Clear[tyList,
   tyFit,par1,s1,s2,s3,label,gr1,gr2,gr,f];*)
   XY = MapThread[List, {X, Y}];
   xyFit = FindFit[XY, model, par, x];
   myVar = Symbol[StringReplace[ToString[x], a_ ~~ "$" ~~ ___ -> a]];
   f[ToExpression[ToString[myVar] <> "_"]] =
    model /. x -> myVar /. xyFit;
   label = StringForm["y=``", f[myVar]];
   If[plotQ,
    gr2 =
     LogLinearPlot[f[x], {x, Min[X], Max[X]}, PlotStyle -> {Thick},
      PlotLabel -> label, GridLines -> Automatic,
      AxesLabel -> axesLabel,
      PlotRange -> {{Min[X], Max[X]}, {0., Max[Y]}}];
    gr1 =
     ListLogLinearPlot[XY, AxesLabel -> axesLabel, PlotLabel -> label,
       Joined -> True, PlotMarkers -> Automatic,
      PlotStyle -> {Dotted(*,PointSize[.02]*)}];
    gr = Show[{gr2, gr1}]
    (*saveImg[gr,fileName];*)
    ];
   Return[{f[myVar], gr}];
   ];

It's not elegant, but it works.

By the way: XY = MapThread[List, {X, Y}] is correct, but I usually use
Transpose[{X,Y}] which is somewhat more compact  (even more so if you use
the {X, Y}\[Transpose] notation, with the transpose symbol generated by
esc-tr-esc).

Cheers -- Sjoerd

> -----Original Message-----
> From: Ted Sariyski [mailto:tsariysk at craft-tech.com]
> Sent: Saturday, 12 February 2011 15:00
> To: 'Sjoerd C. de Vries'
> Subject: RE: how to drop ContextPath when printing from a package?
>
> Hi Sjoerd,
> Thank you for the comments. Actually I also  pass the model as an argument
to
> the module (attached):
>
> bArea[x_]=fit1D[time, area,a+c x^d,{a,c,d},x,{"time [sec]","area
> [m^2]"},"bArea",plotQ];
>
> I have bArea::usage="bArea[t (*sec*)]" in the Package header for further
use of
> bArea.
>
> The second suggestion is not applicable for this mode of use and I am not
sure I
> understand what do you mean with "... to use a different variable in your
> module, so not x, or not to return the fit in terms of x." I tried
something like
> "label = StringForm["y=``", f/.x->t)]" but it did not do the job. Could
you explain,
> please?
>
> Thanks again,
> --Ted
>
>
> fit1D[X_,Y_,model_,par_,x_,axesLabel_,fileName_,plotQ_] :=
>     Module[{XY,xyFit,label,gr1,gr2,gr,f},
>     	(*Clear[tyList,tyFit,par1,s1,s2,s3,label,gr1,gr2,gr,f];*)
>         XY = MapThread[List, {X, Y}];
> 		xyFit = FindFit[XY, model,par,x];
> 		f=model/.xyFit;
>
> 		label = StringForm["y=``", f(*/.x->t*)];
>
>         If[ plotQ,
>            gr2 =
>
LogLinearPlot[f,{x,Min[X],Max[X]},PlotStyle->{Thick},PlotLabel->label,GridLi
> nes->Automatic,
>
> AxesLabel->axesLabel,PlotRange->{{Min[X],Max[X]},{0.,Max[Y]}}];
>            gr1 =
>
ListLogLinearPlot[XY,AxesLabel->axesLabel,PlotLabel->label,Joined->True,Plot
> Markers->Automatic,PlotStyle->{Dotted(*,PointSize[.02]*)}];
>            gr = Show[{gr2,gr1}];
>            saveImg[gr,fileName];
>        ];
>
> 		Return[f];
>     ];
>
>
> -----Original Message-----
> From: Sjoerd C. de Vries [mailto:sjoerd.c.devries at gmail.com]
> Sent: Saturday, February 12, 2011 5:20 AM
> To: Ted Sariyski
> Subject: Re: how to drop ContextPath when printing from a package?
>
> Hi Ted,
>
> I assume your variable is local to a package that contains the variable.
Apart
> from the package context I further assume that your module basically does
> something like:
>
> myFit[data_] :=
>  Module[{x, f},
>   f = FindFit[data, a + b x, {a, b}, x];
>   a + b x /. f
>   ]
>
> which yields something like:
>
> In[276]:= myFit[{{1, 2.2}, {2, 3.8}, {3, 6}, {4, 8.4}}]
>
> Out[276]= -0.1 + 2.08 x$142961
>
> In my opinion, it is never a good idea to return a local variable. One
solution is,
> of course, to use a different variable in your module, so not x, or not to
return
> the fit in terms of x. If returning a model in terms of x is necessary
another
> solution might be
>
> myFit[data_] :=
>  Module[{x, f},
>   f = FindFit[data, a + b x, {a, b}, x];
>   a + b Symbol["x"] /. f
>   ]
>
> In[278]:= myFit[{{1, 2.2}, {2, 3.8}, {3, 6}, {4, 8.4}}]
>
> Out[278]= -0.1 + 2.08 x
>
> Cheers -- Sjoerd
>
>
> On Feb 11, 10:14 am, Ted Sariyski <tsari... at craft-tech.com> wrote:
> > Hi,
> > I have a module, which make use of  FindFit[data,model,par,x] and
> > returns the model and a plot of data and the fit curve. I want to use
> > the model as a PlotLabel but instead of
> >
> > y=1.19623+1048.91 x^0.733809
> >
> >   I  get
> >
> > y=1.19623+1048.91 initData`Private`x$^0.733809
> >
> > How can I  get rid of  the ContextPath  initData`Private`?
> > Thanks in advance,
> > --Ted



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