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I have been using the points of Mathematica plots for more than 25 years and it suddenly does not work any longer in version 11:

gr = Plot[Sin[2 \[Pi] x], {x, 0, 1}]

result of the plot

gr[[0]]

returns Graphics

gr[[1, 1, 1, 3]]

returns

{Directive[Opacity[1.], RGBColor[0.368417, 0.506779, 0.709798], AbsoluteThickness[1.6]], 
Line[{{2.04082*10^-8, 1.28228*10^-7}, {0.000306718, 
0.00192716}, {0.000613415, 0.00385419}, {0.00122681, 
0.0077082}, {0.0024536, 0.0154158}, {0.00490718, 
0.0308278}, {0.00981434, 0.0616262}, {0.0196287, 0.123018},....

The points seem to be there and reachable, but

gr[[1, 1, 1, 3, 2]

returns "ChartingPrivateTag$109972#1" instead of the Line[] with the points!

How to get the points in version 11 (and above)?

Thank you for your help.

Denis

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  • $\begingroup$ Moving my answer to comment, probably more appropriate: it actually works for me (v11.3 on mac osx), I don't get the error: have you tried restarting the kernel? maybe you have some definitions that are creating some conflict.. but it sounds very weird $\endgroup$ – Fraccalo Feb 26 '19 at 11:58
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    $\begingroup$ Try gr[[1, 1, 1, 3, 1, 2]]. The actual list which contains the line primitive is wrapped by an Annotation that can only be seen with FullForm or InputForm. But indeed weird; these Annotation wrappers haven't been there in former versions. $\endgroup$ – Henrik Schumacher Feb 26 '19 at 12:11
  • $\begingroup$ Thank you Fraccalo. My version is 11.1 and I have the problem with a fresh Kernal and only the code above... $\endgroup$ – user3650925 Feb 26 '19 at 12:13
  • $\begingroup$ Thank you Enrik. gr[[1, 1, 1, 3, 1, 2]] works !!! But Why? $\endgroup$ – user3650925 Feb 26 '19 at 12:16
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    $\begingroup$ @user3650925 As I said: The actual Line primitive lies a level deeper because of an (almost) invisible wrapper called Annotation. Have a look at InputForm[gr[[1, 1, 1, 3]]] to see it. $\endgroup$ – Henrik Schumacher Feb 26 '19 at 12:49
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Cases[gr, Line[x_] :> x, -1]
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  • $\begingroup$ This is probably the most robust (and future-proof) approach possible. $\endgroup$ – Henrik Schumacher Feb 26 '19 at 13:03
  • $\begingroup$ ah yes, it is an interesting alternative that will work in any version. Thank you. $\endgroup$ – user3650925 Feb 26 '19 at 13:10
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    $\begingroup$ @HenrikSchumacher Thanks for your comment, I hope so. $\endgroup$ – Αλέξανδρος Ζεγγ Feb 26 '19 at 13:12
  • $\begingroup$ @user: it's not an "alternative"; it's a standard way to extract graphics primitives from a plotting function, which as noted doesn't need to know how deeply the primitves are buried in Graphics[]. $\endgroup$ – J. M.'s ennui♦ Feb 27 '19 at 0:44

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