I plotted box plots for a dataset of >20 million rows. The whiskers came out with little arrows pointing towards the boxes: enter image description here

What do they mean?

  • $\begingroup$ It would be helpful if you could mention the specific software this came from. Best to also add the relevant tag. $\endgroup$ Jun 2, 2020 at 14:45
  • $\begingroup$ The major messages here to me are that you may be better off on a transformed scale and that you have enough data points to look more closely at the distribution using e.g. a kernel density estimate. $\endgroup$
    – Nick Cox
    Jun 2, 2020 at 15:10
  • 1
    $\begingroup$ Those aren't arrows. They are horizontal lines (showing the fences) superimposed on individual point symbols (diamonds). $\endgroup$
    – whuber
    Jun 2, 2020 at 16:45

1 Answer 1


It means nothing. It is a visual artefact of many black wheels overlayed on top black lines.

enter image description here

  • $\begingroup$ I am also thinking of a visual artifact where whiskers combine with points. But why would the points be more like diamond shape than round shape? $\endgroup$ Jun 2, 2020 at 18:08
  • $\begingroup$ @SextusEmpiricus because of low resolution. $\endgroup$
    – Tim
    Jun 2, 2020 at 18:13
  • $\begingroup$ I see now, the whiskers are not only a horizontal a stripe but also a vertical stripe. So the vertical stripe makes the circle a pointy shape. $\endgroup$ Jun 2, 2020 at 20:26

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