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Consider the following code:

fun[x_] := x^2;
Plot[fun[x], {x, -4, 4}]

which simply plots a parabola for the range of -4 to 4. I don't know how many points between -4 and 4 Mathematica uses to plot the function? My question is how can I control this number? In fact I have a complicated function which its evaluation takes a long time. On the other hand I need to plot it in range of 0 to 4 to see its shape. When I try Plot command in the range of {0,4} it takes a very very long time to get the curve (it has never finished), so I want to reduce number of points. I took a look on the options of Plot command but I didn't find my desire one. Any idea?

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  • $\begingroup$ see PlotPoints and MaxRecursion $\endgroup$
    – kglr
    Commented Dec 3, 2020 at 14:58
  • $\begingroup$ try also Plot[Evaluate @ yourcomplicatedfunction[x], {x, -4, 4}] $\endgroup$
    – kglr
    Commented Dec 3, 2020 at 14:59
  • $\begingroup$ @kglr what does Evaluate command do? $\endgroup$
    – Wisdom
    Commented Dec 3, 2020 at 15:14
  • $\begingroup$ Another thing you might try is to define the function as fun[x_] = x^2; (remove the colon before the equals). This may be why the plotting is so slow. $\endgroup$
    – bill s
    Commented Dec 3, 2020 at 15:41
  • $\begingroup$ I meant, just in case, you have a case like this $\endgroup$
    – kglr
    Commented Dec 3, 2020 at 15:44

1 Answer 1

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You can use the options PlotPoints and MaxRecursion. For example

fun[x_] := x^2;
Plot[fun[x], {x, -4, 4}, PlotPoints -> 5, MaxRecursion -> 0]

gives

enter image description here

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  • $\begingroup$ PlotPoints is the number of points? $\endgroup$
    – Wisdom
    Commented Dec 3, 2020 at 15:13
  • $\begingroup$ PlotPoints is the number of initial sampling points. MaxRecursion the number of times the sampling is iterated. As an example, the options PlotPoints -> 5, MaxRecursion -> 0 and PlotPoints -> 2, MaxRecursion -> 2 give the same answer. $\endgroup$
    – Roderic
    Commented Dec 3, 2020 at 15:16

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