Re: Mimicking the TI calculator graph "trace" function

*To*: mathgroup at smc.vnet.net*Subject*: [mg113212] Re: Mimicking the TI calculator graph "trace" function*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Tue, 19 Oct 2010 05:54:26 -0400 (EDT)*Reply-to*: hanlonr at cox.net

Don't know anything about the calculator but this may be close to what you want: f[x_] := (x + 2) (x - 1) (x - 3) Manipulate[ Module[{fp, pt, xdel = 0.1, xmin = -3, xmax = 4}, Plot[f[x], {x, xmin, xmax}, Frame -> True, Epilog -> {Text[ {p, NumberForm[fp = f[p], 3]}, pt = {p, fp}, {If[p < (xmax + xmin)/2, -1.5, 1.5], If[fp < 0, -1, 1]}], If[fp == 0 || Abs[f'[p]] < Abs[f'[p - xdel]] && Abs[f'[p]] < Abs[f'[p + xdel]], Directive[AbsolutePointSize[6], Red], Directive[AbsolutePointSize[4], Blue]], Point[pt]}]], {{p, -3, x}, -3, 4, 0.1, Appearance -> "Labeled"}] Bob Hanlon ---- John Accardi <accardi at accardi.com> wrote: ============= Hello .... I'm trying to find the easiest way to get Mathematica to do what a TI-84 calculator does with the "trace" button on a graph. (displays x,y coordinates at tracing cursor positions). Alternately, I could live with having the intersection point(s) of two graphs dynamically display, with label(s), on a plot, along with the function graphs. I know I can do this in a table of values, but I want to see point and label on the graph plot. This document describes much of it, but you have to hard code the solution point to create the point label: http://amath.colorado.edu/computing/Mathematica/labelpoints/ (The above document contains a link to the *.nb being described.) I guess I am looking for any code that exists where the point label is created dynamically after a solution point is calculated and included in the plot. This seems like a very common thing to want to do but I cannot seem to find anything in the archive/forum that does anything like this. Thanks for any insights. Gianni -- Bob Hanlon