Re: Summary: Which[] as Textbook Input, Plot[] Questions

*To*: mathgroup at smc.vnet.net*Subject*: [mg54072] Re: Summary: Which[] as Textbook Input, Plot[] Questions*From*: "Mariusz Jankowski" <mjankowski at usm.maine.edu>*Date*: Wed, 9 Feb 2005 09:28:01 -0500 (EST)*Organization*: University of Southern Maine*References*: <cua5gn$hhl$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Matt, the answer to your first question is the function Piecewise introduced in version 5 of Mathematica. As to the second, the Plot function evaluates the given function at a discrete set of points to render it on the screen - the selected set of points need not include discontinuities in the function. Regards, Mariusz >>> Matt<anonmous69 at netscape.net> 2/8/2005 5:49:59 AM >>> Hello, I apologize if the answer to this is somewhere glaringly obvious in the documentation, however, after at least 4 hours pawing through both the hardcover Mathematica 4.0 book by Wolfram and the in-program Mathematica 4.1 documentation, I cannot find how I would annotate a function that takes on different values based upon different domains. To wit, something like: Clear[f]; f[x_] := Which[x < 0, Sin[x]/x, x == 0, 1, x > 0, Sin[x]/x]; Plot[f[x], {x, -pi, pi}, AxesLabel -> {"x", "f[x]"}; The 'Which' function is great for actually evaluating something, but I was looking for something along the lines of traditional mathematical notation (such as one would write on a chalkboard or on a sheet of paper), where a large left-bracket would be used and the various definitions of the function for the various ranges would be 'constrained' by the bracket. I'll try to illustrate what I mean, where the '|'s that I will use should be interpreted as a single, large left-bracket: | Sin(x)/x, x < 0 f(x) = | 1, x = 0 | Sin(x)/x, x > 0 Is there a way to do what I'm asking in Mathematica 4.1 (or even above)? As regards the Plot[] function, I'm puzzled as to why the following doesn't give me an error when evaluated: Clear[g]; g[x_] := 1/x; Plot[g[x], {x, -5, 5}]; It seems as though it should, considering that x at zero is undefined. However, Mathematica draws the graph as though the function were just fine. Thanks for any light you can shed on this, Matt