Re: Simple Problem (I suppose...)
- To: mathgroup at smc.vnet.net
- Subject: [mg22127] Re: [mg22102] Simple Problem (I suppose...)
- From: "David Park" <djmp at earthlink.net>
- Date: Wed, 16 Feb 2000 02:34:43 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Hi Andreas, I think you have a lot of newbie errors in entering the characters. 1) Remove["Global`*"] You must use the "backquote" in the upper left hand part of the keyboard. You used the regular quote. Use ` instead of '. 2) f[x_] := x^5 + x^4 + x^2 The thing following the x is the underscore character. You used a subscript. You don't want a subscript here. The plot failed because it had no definition for f[x] and so couldn't get a number value. 3) f2[x_] = D[f[x], x] The same problem here. You need the underscore after the x, and your original f definition was still bad. 4) f2[x] = D[f[x], x] This didn't work because the original f definition was still bad. Also you will generally not wish to make definitions that way because it will only work with x and not other variables. I would recommend working through as much of Part I of the Mathematica Book as you can, typing in each of the statements until you get the hang of entering statements. The two dimensional statements take a little practice. For sending to MathGroup if often helps to convert the cells to InputForm (Ctrl-Shift-I). David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ >Hi! > >I just got Mathematica 4 and when I try such easy calculations as below >and then I can't plot the result.... WHY?? I really have no clue. > >Thanks, > >Andreas. > >Here my text is clipped: >" >In[1]:= >Remove["Global'*"] > >Remove::"rmnsm": "There are no symbols matching \"\!\(\"Global'*\"\)\"." > >In[2]:= >\!\(f[\(x\_-\)] := \ x\^5 + x\^4 + x\^2\) > >In[3]:= >Plot[f[x], {x, -10, 10}]; > >Plot::"plnr": "\!\(f[x]\) is not a machine-size real number at \!\(x\) = >\ >\!\(-9.999999166666667`\)." > >Plot::"plnr": "\!\(f[x]\) is not a machine-size real number at \!\(x\) = >\ >\!\(-9.188660168541684`\)." > >In[4]:= >\!\(f2[\(x\_-\)]\ = \ \[PartialD]\_x f[x]\) > >Out[4]= >\!\(\* > RowBox[{ > SuperscriptBox["f", "\[Prime]", > MultilineFunction->None], "[", "x", "]"}]\) > >In[5]:= >?f2 > >In[6]:= >\!\(f2[x]\ = \ \[PartialD]\_x f[x]\) > >Out[6]= >\!\(\* > RowBox[{ > SuperscriptBox["f", "\[Prime]", > MultilineFunction->None], "[", "x", "]"}]\) >" > >