Bad interaction between Join and ListPlot (or Plot)

Question

When you write this code:

tab = {{1, 1}}; tab = Join[tab, {{2,2}}];

you expect to get the following table:

{{1, 1}, {2, 2}}

but, if you write the following code instead:

tab = {{1, 1}}; tab = Join[tab, {{2, 2}}]; ListPlot[tab]

and after that, you check the elements of tab, it will contain these elements:

{{1, 1}, {2, 2}, {2, 2}}

Why does it happen? Is it a kind of bug of Mathematica, or I do not understand how the Join function works? (I'm running version 10.0.0 on Windows 10.)

That's not what I get. You may need to clear tab. Clear[tab] — Young, Jul 23 '16 at 00:41
I am using Mathematica 10. If you place Clear on the same line, it works. But not if you do it in separate lines. I mean, what you say works if you write: Clear[tab]; tab = {{1, 1}}; tab = Join[tab, {{2, 2}}]; ListPlot[tab] — Francisco, Jul 23 '16 at 00:43
Does this happen on a fresh kernel? What version and OS are you on? — J. M.'s missing motivation, Jul 23 '16 at 00:44
I am in Windows 10. Sorry, what do you mean with fresh kernel? It happens even if I place Clear["Global`*"] in a previous line — Francisco, Jul 23 '16 at 00:47
Sorry Young, I need more input for your answer. Do I have to search for that in a CMD? — Francisco, Jul 23 '16 at 00:50
Sorry, to insist. Did you try what I posted? Which version and OS are you using? — Francisco, Jul 23 '16 at 00:53
Yes, I ran your code without issue. (I'm using Windows 7, 64-bit, V10.4) — Young, Jul 23 '16 at 00:55
Ok. Do not worry then. I will not put ListPlot after that. I can not be checking everytime I update my OS or Mathematica if it still happens — Francisco, Jul 23 '16 at 00:56
Yes, I made a fresh document just to be sure, that only contains those lines. And I still have that problem. — Francisco, Jul 23 '16 at 00:59
I can confirm this problem in Mathematica 10.0.0. The strangest thing I ever saw. — C. E., Jul 23 '16 at 01:15
Yes, I have the very same version 10.0.0. As I said before, it is a pain to be looking for this issue in every new version. I think that I will adopt as a practice not to write that extra line to be in the safe zone. Thank you all for your help. — Francisco, Jul 23 '16 at 01:19
Do not use 10.0.0. Upgrade at least to 10.0.2, which should be a free upgrade to you. Upgrade to the latest version if you have access. — Szabolcs, Jul 23 '16 at 12:49
I would put money on the damn Suggestions Bar (Predictive Interface) being the culprit. *Turn it off!* @C.E. Can you confirm? — Mr.Wizard, Jul 23 '16 at 14:14
It's sad that such things happen. But is good to know the solution. Thank you @Mr.Wizard — Francisco, Jul 24 '16 at 13:37

score 9 · Accepted Answer · edited Apr 13 '17 at 12:56

9

As Mr. Wizard wisely suggested in his comment, the Suggestion Bar feature is the source of this bug. I have confirmed that turning it off removes the bug.

The canonical answer for Suggestion Bar troubles is found here. It shows how to turn it off, under Preferences > Interface.

edited Apr 13 '17 at 12:56

Community

1

answered Jul 23 '16 at 17:59

C. E.

70,533
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It solved the problem, thank you. – Francisco Jul 24 '16 at 13:35

Bad interaction between Join and ListPlot (or Plot)

1 Answers1