Re: Novice question regarding variable naming and subscripts

*To*: mathgroup at smc.vnet.net*Subject*: [mg28188] Re: [mg28136] Novice question regarding variable naming and subscripts*From*: Tomas Garza <tgarza01 at prodigy.net.mx>*Date*: Tue, 3 Apr 2001 02:38:06 -0400 (EDT)*References*: <200103310759.CAA13165@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Don't use "blank", i.e., the underscore "_", to "imply a subscript". It has a well-defined mission in Mathematica. I suggest you use the basic input palette to write F-subscript and it is much easier. Then (in input form) it reads In[1]:= Subscript[F, i][F_] := F + a/2 and your plot will appear with Plot[Evaluate[Subscript[F, i][F] /. a -> 1], {F, 0, 10}]; Copy this into your notebook, and convert the cells to StandardForm: select each cell and then Cell|ConvertTo|StandardForm so that the notation you want to use shows properly. Tomas Garza Mexico City ----- Original Message ----- From: "William McHargue" <William at McHargue.Com> To: mathgroup at smc.vnet.net Subject: [mg28188] [mg28136] Novice question regarding variable naming and subscripts > Hello to The Math Group, > > I am new to this group and have a burning question about Mathematica > use. (I hope to give back to the group when I have something to > contribute, but presently I'm still somewhat of a novice.) > > In some ways you could call me a "casual" user of Mathematica. I pick it > up when a project demands, but often never get REALLY good at it. > Typically I like to use it to both document and define a simulation or > model. I would like to use the full 2D-input to define the various > equations involved, but there seems to be a problem when I define, say, > a function: > > F_i[F_]:=F+(a/2); > > (where "F_i" implies "F" subscript "i") > > Then I wish to, say, plot this function using a variable "F" (no > subscript) using this: > > Plot[ F_i[F]/.a->1, {F, 0, 10}] > > When this is evaluated it says: > > Plot::"plnr" : F_i[F]/.a->1 is not a machine-size real number at... > > (over and over again, and at valid values) > > Yet, it works fine if I pick a different independent variable. I realize > I could use just "x" instead of "F", but by keeping the actual Input > Form reading like the common equations in particular applications the > whole thing is much easier to follow and debug. > > I wouldn't be surprised if I do not fully understand the way Mathematica > manages its name space, but I would like subscripted names to be > completely independent from their non-subscripted brothers--the way we > humans might write equations and variables on paper. > > Any ideas, or perhaps chapters in the documenation I should dive into > more deeply? > > Thanks in advance for any info in this regard, > > > Bill. > > -- > William B. McHargue - Physicist > <mailto:William at McHargue.Com> > Yahoo/Jabber IM: William_McHargue >