# Skipping or changing one grid line

I'm trying to plot normalized data in a bar chart. To better show that the data is normalized, I want the horizontal grid line at 1 to look differently, eg. dashed instead of dotted.

I guess this can be done by (1) changing the style of a single grid line (which I have no idea how to do) or by (2) manually adding the line at 1 (which I managed to do) and skipping the grid line so that the lines are not drawn over each other (which I, again, do not know how to do).

This is my MWE for the second case:

\documentclass{article}

\usepackage{tikz}
\usepackage{pgfplots}
\usepackage{pgfplotstable}

\usetikzlibrary{backgrounds}

\pgfplotsset{compat=1.8}

\begin{document}

\begin{tikzpicture}

Model       runtime normalized
(1)     0.17    0.11
(2)     1.60    1.00
(3)     3.17    1.98
(4)     1.72    1.08
(5)     4.01    2.51
}\data

\begin{axis}[
ybar,
ymin=0,
xtick=data,
xticklabels from table={\data}{Model},
grid style={dotted,gray},
ymajorgrids=true,
nodes near coords,
]

\addplot [draw=black,fill=gray!15] table [y=normalized,x expr=\coordindex] {\data};
\begin{scope}[on background layer]
\draw [dashed] ({rel axis cs:0,0}|-{axis cs:0,1}) -- ({rel axis cs:1,0}|-{axis cs:0,1});
\end{scope}

\end{axis}
\end{tikzpicture}

\end{document}


This results in the following:

Here, the grid line for the value 1 is still drawn, and its dots appear between the dashes of my manually added line, which looks ugly to me.

-

One way to do it is to specify all yticks except 1 and then use the extra y ticks and extra y ticks style to add the tick at y=1 and to change the grid style only for that tick.

\documentclass{article}

\usepackage{tikz}
\usepackage{pgfplots}
\usepackage{pgfplotstable}

\usetikzlibrary{backgrounds}

%\pgfplotsset{compat=1.8}

\begin{document}

\begin{tikzpicture}

Model       runtime normalized
(1)     0.17    0.11
(2)     1.60    1.00
(3)     3.17    1.98
(4)     1.72    1.08
(5)     4.01    2.51
}\data

\begin{axis}[
ybar,
ymin=0,
xtick=data,
ytick={0.5,1.5,2.0,2.5},
extra y ticks=1,
extra y tick style={grid=major, grid style={dashed,black}},
xticklabels from table={\data}{Model},
grid style={dotted,gray},
ymajorgrids=true,
nodes near coords,
]

\addplot [draw=black,fill=gray!15] table [y=normalized,x expr=\coordindex] {\data};

\end{axis}
\end{tikzpicture}

\end{document}


-