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MathGroup Archive 2000

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Re: Plotting multiple functions using Map

  • To: mathgroup at smc.vnet.net
  • Subject: [mg24291] Re: [mg24254] Plotting multiple functions using Map
  • From: Matt.Johnson at autolivasp.com
  • Date: Fri, 7 Jul 2000 00:11:32 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com


Per Section 1.9.1:

There are, however, some cases in which it is much better to have Mathematica
evaluate f before it starts to make the plot. A typical case is when f is
actually a
command that generates a table of functions. You want to have Mathematica first
produce the table, and then evaluate the functions, rather than trying to
produce
the table afresh for each value of x. You can do this by typing Plot[Evaluate[ f
 ],{x, xmin, xmax}].

This works:

Plot[Evaluate[Map[f[x,#1]&,ylist]],{x,-3,3}]

-matt






Grischa Stegemann <Stegemann at Physik.TU-Berlin.DE> on 07/05/2000 09:10:36 PM

Subject: [mg24291]  [mg24254] Plotting multiple functions using Map




Dear group

I have a two parameter function, e.g.
In[1]:= f[x_,y_]:=x+y

Now I would like to plot f[x,y1],f[x,y2],... within the same chart.
Usually you would try something like this:
In[2]:= Plot[{f[x,1],f[x,2],f[x,3]},{x,-3,3}]

Since my list of y's is pretty long I tried this:
In[3]:= ylist={1,2,3};
        Plot[Map[f[x,#1]&,ylist],{x,-3,3}]

but Mathematica complains
  Plot::"plnr": (f[x, #1]&)/@ylist is not a machine-size real number
                at x=-2.9999997

On the other hand we have
In[4]:= Map[f[x,#1]&,ylist]
Out[4]= {1 + x, 2 + x, 3 + x}
and
In[5]:= Plot[{1 + x, 2 + x, 3 + x},{x,-3,3}]
of course works as expected.

Where is my mistake?
--
                         Grischa

----------------------------------------------------------------------
Grischa Stegemann                       Technische Universitaet Berlin
email: Stegemann at physik.tu-berlin.de

*** We are here on Earth to do good for others.
*** What the others are here for, I do not know.  (W.H. Auden)







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