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Using Tooltip, is it possible to display the numeric value of the curve I've plotted using Plot and PolarPlot?

For example, is it possible to display the numeric y value of Sin[x] (or any other curve) with Tooltip?

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2 Answers 2

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I thought I did something like the following before, but maybe it was not for this site:

DynamicModule[{y0},
 EventHandler[
  Plot[Tooltip[Sin[x], Dynamic[y0]], {x, 0, 2 Pi}],
  "MouseMoved" :> (y0 = Sin@First@MousePosition["Graphics"]),
  ]]

Update, per comment. Note that MousePosition["Graphics"] returns the coordinates of the mouse, not of a point on the graphics. It is triggered when the mouse is near the graphics, so it gives only a very rough approximation to the function value. One can take the x-coordinate of the mouse as given and calculate the y-coordinate from the function. If the function is complicated, one might not want to copy the code into both arguments of Tooltip; I use With below so one needs only to type the function expression once. (There's a red syntax warning on the x inside Dynamic, because Dynamic is HoldFirst and Plot effectively uses Block to assign x a value; but it's just what we need here, since Plot finishes evaluating before Dynamic reaches the front end.)

With[{f = Sin[x]},
 Plot[
  Tooltip[f,
   Dynamic[f /. x -> First@MousePosition["Graphics"]]],
  {x, 0, 2 Pi}]
 ]

Bells & whistles:

With[{f = Sin[x]},
 DynamicModule[{x1, y1},
  EventHandler[
   Plot[
    f,
    {x, 0, 2 Pi},
    MaxRecursion -> 0,
    Epilog -> {Red, Dynamic@Tooltip[Point[{x1, y1}], {x1, y1}]},
    GridLines -> {
      Dynamic@If[NumericQ[x1], {x1}, None],
      Dynamic@If[NumericQ[y1], {y1}, None]}
    ],
   "MouseMoved" :> (
     x1 = First@MousePosition["Graphics", {x1, 0}];;
     y1 = f /. x -> x1)],
  Initialization :> (
    x1 = Pi; y1 = f /. x -> Pi)]]
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  • 6
    $\begingroup$ for minimal functionality this is enough Plot[Tooltip[Sin[x], Dynamic@MousePosition["Graphics"]], {x, 0, 2 Pi}] $\endgroup$
    – Kuba
    Jul 14, 2016 at 18:38
  • $\begingroup$ @Kuba D'oh! Thanks! (You can answer with that, if you like. But I'm tempted to close as dupe....) $\endgroup$
    – Michael E2
    Jul 14, 2016 at 18:53
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Potential way to achieve this:

pl = Plot[Sin[x], {x, 0, 10}];
vals = Table[Tooltip[{x, Sin[x]}, Sin[x]], {x, 0, 10, .05}];
lp = ListPlot[vals, PlotStyle -> None];
Show[{pl, lp}]
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