Here is the code:

Dynamic@Show[{Graphics[{LightGray, Rectangle[{0, -1}, {Pi, 1}]}], 
   Plot[Sin[a x], {x, 0, Pi}]}]

The Slider controls the value of a in Plot[] to produce a dynamic plot of Sin[]. I would like to make the Plot[] dynamic only, but it didn't work if i only wrapped plot[] with dynamic[], so i added dynamic to the whole show[]. So how to dynamically update plot[] solely?

  • $\begingroup$ Manipulate[Plot[Sin[a x], {x, 0, π}, PlotRange -> {{0, π}, {-1, 1}}, Prolog -> {LightGray, Rectangle[{0, -1}, {π, 1}]}], {{a, 1}, -2, 2, 0.01, Appearance -> "Labeled"}] $\endgroup$ – Bob Hanlon Sep 19 '20 at 4:46
  • $\begingroup$ the code i posted in the question is a simplified example, the original code has combined graphics and plot, so it's unlikely to modify it by using Prolog. $\endgroup$ – DORA Sep 19 '20 at 4:59
  • $\begingroup$ Besides, the Prolog will be updated as well while the value of a changes, right? Because the whole Plot is dynamic. $\endgroup$ – DORA Sep 19 '20 at 5:06
  • $\begingroup$ Slider[Dynamic[a]] gr = Graphics[{LightGray, Rectangle[{0, -1}, {Pi, 1}]}]; Dynamic[Show[gr, Plot[Sin[a x], {x, 0, Pi}]]] $\endgroup$ – Bob Hanlon Sep 19 '20 at 5:24

You can evaluate the Graphics expression in place, so that it just becomes a constant in the Show expression. Like so:



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