When I add a Line or a point to a ListLogPlot using for example Show[plot,Graphics[Line[{{0,0.1},{100,0.1}}] it does not appear where I put it but instead -Exp[#]& gets applied to the y coordinates. So in this case the line appears around 0.905. How do I add graphics at the actual points I want to add them?

  • 1
    $\begingroup$ Perhaps you could use the GridLines option of ListLogPlot instead? For example, GridLines->{{}, {.1}} $\endgroup$
    – Carl Woll
    Mar 4, 2021 at 16:23

1 Answer 1

plot = ListLogPlot[Table[PartitionsQ[n], {n, 50}], 
  Joined -> True];

On a log plot the y coordinate cannot be zero. Whatever y value is intended, you need to take its log. For either vertical or horizontal lines, InfiniteLine (introduced in version 10) is the easiest way to span the full plot.

  Graphics[{Red, InfiniteLine[{{1, Log[20]}, {10, Log[20]}}],
   Green, InfiniteLine[{{30, 1}, {30, 10}}]}]]

enter image description here

  • $\begingroup$ I already edited the question to point out that 0.1 would be a better example I can also edit it in the main text if preferred. Note that the point stands for any number greater than 0. It is in my opinion a crazy choice of MMA to implement things this way and I would like a real work around, rather than applying Log to everything I might ever add to a plot. Note that if for example I want to add points at coordinates I picked (using .) I would have to first apply Log to them. That would be a major inconvenience. $\endgroup$
    – Kvothe
    Mar 4, 2021 at 13:49
  • $\begingroup$ To add points use Point[{#[[1]], Log[#[[2]]]} & /@ points] $\endgroup$
    – Bob Hanlon
    Mar 4, 2021 at 14:47

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