Refresh plot during heavy calculations

Question

I have some heavy calculations with generates huge list of {x, y} points. I want to dynamically update plot during calculations. Or update it after calculations complete. I can't use simple Dynamic @ Plot, because it makes calculation time 5-10x times longer. So I made some example, how I tried to solve this problem. But it didn't work.

Manipulate[None, 
  Grid[
    {{Dynamic[
        ListPlot[
          Refresh[pts, UpdateInterval -> 5], 
          PlotRange -> All], 
        UpdateInterval -> 2], 
      SpanFromLeft, 
      SpanFromLeft}, 
     {Slider[Dynamic[a], {10, 20, 1}], 
      Dynamic@ProgressIndicator[i, {1, a}], 
      Button["Run", func[], Method -> "Queued"]}}], 
  TrackedSymbols :> {}, 
  ContinuousAction -> False, 
  SynchronousUpdating -> False, LocalizeVariables -> True, 
  Initialization :> (
    pts = {{0, 0}}; a = 10; i = 1; 
    func[] := 
     Module[{}, 
       For[i = 1;, i < a, i++, Pause[.5]; AppendTo[pts, {i, i}]]])]

So how can I refresh plot only every n seconds? Or refresh after all calculations complete?

Answer 1

Your Manipulate expression works for me when I change your button specification to

Button["Run", pts = {{0, 0}}; func[], Method -> "Queued"]

However, I think it would better to replace your unnecessarily complicated Manipulate expression with a simple DynamicModule expression.

DynamicModule[{pts = {{0, 0}}, a = 10, i = 1, func},
  func[] := Do[Pause[.5]; AppendTo[pts, {i, i}], {i, a}];
  Dynamic @ Grid[
    {{ListPlot[pts, PlotRange -> All], SpanFromLeft, SpanFromLeft},
     {Slider[Dynamic[a], {10, 20, 1}], 
      ProgressIndicator[i, {1, a}],
      Button["Run", pts = {{0, 0}}; func[], Method -> "Queued"]}}]]

Answer 2

Option 1: Use the UpdateInterval option to Dynamics, i.e.,

Dynamic[Plot[...],UpdateInterval->n,TrackedSymbols->{}]

where n is measure in seconds. Here, UpdateInterval is how often Dynamic "manually" updates the expression. By default it will also update it any time one of the symbols is changed, so you also need to set TrackedSymbols->{}.

Option 2: Use a dummy dataset in the Dynamics function, and only update that variable at the desired pace. For example,

Print[Dynamic[Plot[dummyData,...]]]; ...calculation code...; dummyData=newData;

Answer 3

Though similar to @Jess's answer, I think this will work as you want.

Dynamic[PLOT,UpdateInterval->10,TrackedSymbols->{}]

Because UpdateInterval only set the Max Update interval!! So as your data is updating at a almost crazy speed, the plot will sense the change of your data and update crazily as well. You have to manually tell Dynamic: don't track data, simply follow the UpdateInterval!!!

Hope this can help u.