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My goal is to draw dots whose positions can be adjusted. I could draw a fixed number of dots, say 2 and 5, like the code below. If the user sets the number of dots, how do I create dots and sliders according to that number?

Manipulate[
 NumberLinePlot[{a, b}, PlotStyle -> {Black, Red}, 
  PlotRange -> {0, 4}], {{a, 1.5}, 0, 4}, {{b, 1}, 0, 4}]

enter image description here

Manipulate[
 NumberLinePlot[{a, b, c, d, e}, PlotStyle -> {Black, Red}, 
  PlotRange -> {0, 4}], {{a, 1.5}, 0, 4}, {{b, 1}, 0, 4}, {{c, 1.2}, 
  0, 4}, {{d, 1.3}, 0, 4}, {{e, 1.4}, 0, 4}]

enter image description here

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1 Answer 1

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9
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The easiest way is to use a nested Manipulate:

DynamicModule[{numbers},
 Manipulate[
  Manipulate[
   NumberLinePlot[Lookup[numbers, Range[n], 0],
    PlotStyle -> {Black, Red}, PlotRange -> {0, 4}],
   Column[
    Slider[Dynamic[numbers[#]], {0, 5}] & /@ Range[n]
    ]
   ],
  {n, 1, 10, 1},
  Initialization :> (numbers = <||>)
  ]
 ]
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2
  • 1
    $\begingroup$ Clever. Where did you find that the controls are placed in an association by specifying: Initialization :> (numbers = <||> $\endgroup$
    – Daniel Huber
    Commented Sep 13, 2023 at 15:57
  • 1
    $\begingroup$ @DanielHuber I don't remember, but when you have something like Slider[Dynamic[expr], ...], you get a control that continuously evaluates expr = controlSetting. So if the expression points to the part of an association or a list, it just uses Part assignment like it normally does. $\endgroup$
    – Sjoerd Smit
    Commented Sep 13, 2023 at 16:22

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