I was trying to improve the solution atDrawing lines in a plot and give them a label? by using Jake's answer atHow to access \xmin, \xmax, \ymin, \ymax from within PGFplots axis environment.So, Jake's answer produces the brown dotted line (the x-axis) with

(current axis.left of origin) -- (current axis.right of origin)

I thought a simple use oftikz'scalc library would allow me to adjust the vertical position of the horizontal line. If I want a horizontal line aty=12, for example, I simply use

($(current axis.left of origin)+(axis cs: 0,12)$) -- ($(current axis.right of origin)+(axis cs: 0,12)$)

where I have applied a+ (axis cs: 0,12) and same for the other coordinate.

Well, that is great in theory, but doesn't work. Instead, it produces the dashed line in red (which is only half the desired line):

Notes:

• Instead of doing coordinate calculations, I also tried applyingshift={(axis cs: 0,12)} option but that had no effect on the output.

Code:

\documentclass{article}\usepackage{pgfplots}\usetikzlibrary{calc}\begin{document}\begin{tikzpicture}\begin{axis}    \addplot {x*x};        \draw [ultra thick, dotted, draw=brown]         (current axis.left of origin) --         (current axis.right of origin);            \draw [ultra thick, dashed, draw=red]         ($(current axis.left of origin) +(axis cs: 0,12)$) --         ($(current axis.right of origin)+(axis cs: 0,12)$);\end{axis}\end{tikzpicture}\end{document}

• 4
  I think you have to useaxis direction cs in this case

  Jake

  – Jake

  2014-03-21 16:10:42 +00:00

  CommentedMar 21, 2014 at 16:10
• @Jake: Yep that works. Please post that as an answer. Some info re:axis cs andaxis direction cs would be useful as well.

  Peter Grill

  – Peter Grill

  2014-03-21 19:05:43 +00:00

  CommentedMar 21, 2014 at 19:05

1 Answer1

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