I want to label the local maxima, local minima, and points of inflection on a plot of a curve. How is this done in Mathematica?
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3$\begingroup$ Have you tried anything? Do you have an example function? $\endgroup$– J. M.'s persistent exhaustion ♦Oct 10, 2018 at 4:12
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1 Answer
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One way to produce such labeling as you ask for is to use Callout. However, Callout only works in plots and not in graphic directives. This complicates things a little because Epilog can't be used to show the points. I resort to plotting the curve on one plot and the critical points and their labels on another and then combining the two with Show.
Here is an example using a cubic polynomial as the curve.
f[x_] := x (x - 1) (x + 1)
pts = {#, f[#]} & /@ {-(1/Sqrt[3]), 0, 1/Sqrt[3]} // N;
lbls = {"max", "inflection", "min"};
places = {Automatic, Automatic, {.63, -.43}};
pts are the critical points
lbls are their labels
places are where they will be placed. Note that I only override Mathematica's automatic placement for the minimum. I was OK with the placement of the other two points. BTW, the point {.63, -.43} will be the position of the kink in the leader line of the minimum's callout.
With[{max = 1},
curve = Plot[f[x], {x, -max, max}];
points =
ListPlot[MapThread[Callout[#1, #2, #3] &, {pts, lbls, places}],
PlotRange -> {{-max, max}, Automatic},
PlotStyle -> {Red, AbsolutePointSize[8]}]];
Show[curve, points, PlotRange -> All]
answered Oct 10, 2018 at 5:29
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$\begingroup$ I upvoted for going beyond what the OP provided. $\endgroup$ Oct 10, 2018 at 7:06
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2$\begingroup$ @J.M.issomewhatokay. I had to because the OP essentially provided nothing. :-) $\endgroup$ Oct 10, 2018 at 14:36