Re: Making plots using transformation rules

*To*: mathgroup at smc.vnet.net*Subject*: [mg71950] Re: Making plots using transformation rules*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Tue, 5 Dec 2006 06:04:54 -0500 (EST)*Organization*: The Open University, Milton Keynes, UK*References*: <el128e$5h8$1@smc.vnet.net>

amannuc at yahoo.com wrote: > I've read about making plots of functions, for example: > > Plot[Evaluate[f[x]], {x, 0, 10}] > > I don't have this sort of function to plot. Because it involves > derivatives, I only get numerical output after defining a > transformation rule. A simple example (not the real one) is the > following: > > g[t_] := D[t^2, t] > g[t] /. t -> 1 > > I cannot evaluate g[1], because then Mathematica thinks I am trying to > take a derivative with respect to the number 1, and flags that as > error. So I need the transformation rule to get function values. > > What is the best way to plot g[t]? I am looking to create multiple > transformation rules that replace the argument t with a reasonable > range of values. Then I can plot g[t] versus t. Plot will not do this > directly because it takes variable values as input. However, as I've > said, the construction g[x] (x = some number) flags an error. > > Thanks for your help. > If the argument is always a number, you could define g[t] with a Set rather than a SetDelayed, or evaluate the derivative directly within the plot command. In[1]:= g[(t_)?NumberQ] = D[t^2, t]; g[1] Plot[g[x], {x, 0, 10}] Out[2]= 2 Out[3]= Graphics In[4]:= Plot[Evaluate[D[t^2, t]], {t, 0, 10}] Out[4]= Graphics Regards, Jean-Marc