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Re: Re: Constructing a Label

  • To: mathgroup at smc.vnet.net
  • Subject: [mg93433] Re: [mg93399] Re: Constructing a Label
  • From: "David Park" <djmpark at comcast.net>
  • Date: Fri, 7 Nov 2008 06:02:59 -0500 (EST)
  • References: <gepb15$sfr$1@smc.vnet.net> <24955424.1225964460341.JavaMail.root@m02>

f[x_] := 2/3 Sin[x^2];

I would consider the first method to be the best:

Row[{"f[x] = ", f[x]}]

This is because it is the most direct and intuitive. The second method
involves descending in to box structure programming, which the new features
of Version circumvent.

The third method with HoldForm is also ok, but if f is define within a
Module with f being a Module variable, then you won't like the result
because it won't be a simple 'f'.

The StringForm method is a nice trick, but it is not as versatile or
intuitive as the Row method.

The last method is too arcane and too old fashioned. ToString, by default,
formats to the old OutputForm, which uses multiple lines for the 3D form of
expressions. That's why you have to specify TraditionalForm or StandardForm.
If you look at the FullForm of the ToString expression you will see that
Mathematica uses the lower level specification for boxed structures:

ToString[TraditionalForm[f[x]]] // FullForm
"\!\(TraditionalForm\`\(2\\ \(\(sin(\(\(x\^2\)\))\)\)\)\/3\)"

Using Column and Row to build up displays is a nice new method in Version 6
and it's worthwhile getting to know how to use them.


David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark 



From: Nikolaus Rath [mailto:Nikolaus at rath.org] 

Nikolaus Rath <Nikolaus at rath.org> writes:
> Hello,
>
> I want to automatically construct labels of the form
> "A = <value of A>" for a number of plots.
>
> However, I cannot quite figure out how to generate the above
> expression.

I have now received quite a number of different solutions for this
problem (now for some general function f[x]):

f[x_] := 2/3 Sin[x^2];
Row[{"f[x] = ", f[x]}]
DisplayForm[RowBox[{"f[x] = ", f[x]}]]
HoldForm[f[x]] == f[x]
StringForm["f[x] = ``", f[x]]
"f[x] = " <> ToString[TraditionalForm[f[x]]]

While they all seem to work equally well for my problem, I do not
quite understand how the last two expressions can actually work out. I
thought that a String is just a sequence of unicode characters, so how
is it possible that it renders as true fraction?


Moreover, this really made me curious in which way the above
expressions differ. The only difference that I found when evaluating
them is that the last one (obviously) only renders in traditional form
and that HoldForm only works if I use == instead of =. But are there
other differences? An should I prefer some variant over the others?


Personally, the variant with HoldForms seems most natural to me,
because it directly expresses what I want to do ("print f[x] in
evaluated and unevaluated form").

         

I'd be interested  in hearing other opinions about this.


Best,

   -Nikolaus

--
 =C2=BBIt is not worth an intelligent man's time to be in the majority.
  By definition, there are already enough people to do that.=C2=AB
                                                         -J.H. Hardy

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