Re: Question about Manipulate

*To*: mathgroup at smc.vnet.net*Subject*: [mg122766] Re: Question about Manipulate*From*: George Woodrow III <georgevw3 at mac.com>*Date*: Thu, 10 Nov 2011 06:51:17 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <201111091124.GAA11113@smc.vnet.net>

You need to learn *some* Mathematica Syntax Define your function with a parameter list, and delayed execution. In your case, f has 3 variables, and should be defined as f[x_, a_, b_] := Sin[a x + b] The way you have write it, f is defined as the (constant) expression that takes whatever values of x, a, and b are defined at the moment f was created. Since these are undefined, f would always return the same expression, which never takes on a numerical value. When you place the expression Sin[a x + b] inside the Plot function, you specify the (local) variables x, a, b as part of the plot and Manipulate functions. geo3rge On Nov 9, 2011, at 6:24 AM, mailcwc at gmail.com wrote: > I tried the following code in Mathematica 8.0 > > Clear["Global`*"] > f = Sin[a x + b] > Manipulate[Plot[f, {x, 0, 4 \[Pi]}], {a, 0.5, 2}, {b, 0, 2 \[Pi]}] > > The Manipulate block is showed, but the Sin function is not plotted. > > When I replace f in the third line with its definition, > > Clear["Global`*"] > Manipulate[ Plot[Sin[a x + b], {x, 0, 4 \[Pi]}], {a, 0.5, 2}, {b, 0, 2 > \[Pi]}] > > The Sin function is plotted. > > Is this a bug or a limitation in Mathematica? >

**References**:**Question about Manipulate***From:*"mailcwc@gmail.com" <mailcwc@gmail.com>