Bug introduced in 10.0 and persisting through 11.0.1 or later

Possible bug? Or am I missing something / expecting too much?

Forgive the seemingly obscure data points but they're where I've noticed a problem.

data = {
   {{(10 π)/8, 1}, ErrorBar[0.2]},
   {{(11 π)/8, 1}, ErrorBar[0.2]},
   {{(12 π)/8, 1}, ErrorBar[0.2]}

ErrorListPlot won't plot the error bar at x = 11 Pi/8 unless the datapoint is first converted to a numerical value:

ErrorListPlot[data, PlotRange -> {{3, 5}, All}]

enter image description here

ErrorListPlot[N@data, PlotRange -> {{3, 5}, All}]

enter image description here

What gives?

  • 2
    $\begingroup$ Definitely a bug, and a weird one. Shorter test code to see the result, Needs["ErrorBarPlots`"]; ErrorListPlot[{{{(# π)/8, 1}, ErrorBar[0.2]}}] & /@ {10, 11, 11.0, 12}. Seems to affect versions 10.x, but works as expected in version 9. $\endgroup$
    – Jason B.
    Commented Mar 30, 2016 at 12:11
  • $\begingroup$ Added the version-10 tag Confirmed what @JasonB said before: works OK on v9 $\endgroup$ Commented Mar 30, 2016 at 13:49

1 Answer 1


(All observations apply to version 10.1.0.)

ErrorListPlot is written in as a rather straightforward post-processing of ListPlot, with error bar values first assigned to and then retrieved from a definition upon ErrorBarPlots`Private`error (hereafter notated error). A definition is made as a side-effect within a replacement rule:

{x_?NumericQ, y_?NumericQ, e_?NumericQ} :>
  (error[N[{x, y}]] = ErrorBar[{0, 0}, {-1*e, e}]; {x, y})

Note that N[{x, y}] is used for the definition but {x, y} is the actual result of the replacement, and this expression is later passed to ListPlot.

After ListPlot post-processing it is applied to point coordinates which includes:

{l, (ebfunc[#1, error[#1]] &) /@ Cases[l, {_?NumericQ, _?NumericQ}, ∞]}

Where l is a Line or Point expression in the plot returned by ListPlot as matched by ReplaceAll.

Making assignments upon numeric values is always a little bit fragile. Here the assumption is that ListPlot will numericize the values plotted in exactly the same way as N[{x, y}] and not modify them further in any way, and it appears that assumption is false.

A "quick fix" for this problem is to apply N to the argument passed to ListPlot within the definition of ErrorListPlot, which may be patched with:

With[{dv := DownValues[ErrorListPlot]},
  dv = dv /. (lp : ListPlot)[a_, x___] :> lp[N @ a, x];

ErrorListPlot[data, PlotRange -> {{3, 5}, All}]

enter image description here

However this still makes the assumption that numeric values passed to ListPlot will appear unchanged in the output Graphics expression, and I don't know if that can be assured now and in the future. I feel that ErrorListPlot should have been written differently, using a wrapper like Annotation as shown in Coloring Points in a Plot, based on their position in the list.

Strangely prior exploration indicated that ListPlot is already set up to use Charting`ErrorBar as a wrapper (like Annotation). Perhaps this has been implemented in more recent versions? (I am still using 10.1.0 as noted earlier.)

  • $\begingroup$ Thanks for the wonderful insights! It's always interesting (and informative) to peek beneath the hood. $\endgroup$ Commented Jul 17, 2016 at 10:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.