You can use
y filter/.expression={y==0 ? nan : y}
in the options of \addplot.
\documentclass{article}
% ---------------------------------- tikz
\usepackage{pgfplots} % to print charts
\pgfplotsset{compat=1.12}
\begin{document}
\begin{figure}
\centering
\begin{tikzpicture}
\begin{axis} [
% general
ybar,
scale only axis,
height=0.5\textwidth,
width=1.2\textwidth,
ylabel={\# Dots},
nodes near coords,
xlabel={Variation},
xticklabel style={
rotate=90,
anchor=east,
},
%enlarge x limits={abs value={3}},
]
\addplot+[y filter/.expression={y==0 ? nan : y}] table [
x=grade,
y=value,
] {
grade value
-11 0
-10 0
-9 0
-8 0
-7 0
-6 0
-5 3
-4 1
-3 2
-2 15
-1 11
0 179
1 8
2 1
3 0
4 1
5 2
6 0
7 0
8 0
9 0
10 0
11 0
};
\end{axis}
\end{tikzpicture}
\end{figure}
\end{document}
In the answer to the linked question, you will see xtick is used for positive values of x, while extra x ticks is for the negative values of x. You need to do something similar here. (I removed a couple unnecessary packages as well.)
\documentclass{article}
\usepackage{pgfplots}
\begin{document}
\begin{figure}[tb]
\begin{tikzpicture}[baseline] \begin{axis}[
ylabel style={rotate=-90},
xtick = {2},
xticklabels = {$ E_{ \mathrm{t2}} $},
grid = major,
ytick = 0,
xmin = -5,
xmax = 5,
ylabel={$I$},
xlabel={$U$},
extra x ticks = {-2},
extra x tick labels = {$ -E_{ \mathrm{t}} $},
extra x tick style = { grid = major,xticklabel style={yshift=0.5ex, anchor=south}
},
axis y line=middle,
axis x line=middle,
]
\addplot[blue,samples=21]
coordinates {
(-5,-5)
(-2,-1)
(2,1)
(5,5)
};
\end{axis}%
\end{tikzpicture}%
\end{figure}
\end{document}
Edit:
One way to get a third tick that is different from the other two is to define a second set of axes with the same limits as the first, and then add the ticks to the new axes.
\documentclass{article}
\usepackage{pgfplots}
\begin{document}
\begin{figure}[tb]
\begin{tikzpicture}[baseline]
\begin{axis}[
ylabel style={rotate=-90},
xtick = {2},
xticklabels = {$ E_{ \mathrm{t2}} $},
grid = major,
ytick = \empty,
xmin = -5,
xmax = 5,
ylabel={$I$},
xlabel={$U$},
extra x ticks = {-2},
extra x tick labels = {$ -E_{ \mathrm{t}} $},
extra x tick style = { grid = major,xticklabel style={yshift=0.5ex, anchor=south}
},
axis y line=middle,
axis x line=middle,
]
\addplot[blue]
coordinates {
(-5,-5)
(-2,-1)
(2,1)
(5,5)
};
\end{axis}%
\begin{axis}[
xmin = -5,
xmax = 5,
xtick = {4},
ytick = \empty,
xticklabels = {$ E_{ \mathrm{t4}} $},
xticklabel style={blue,yshift=0.5ex, rotate=30},
axis x line=middle,
axis y line=middle,
]
\addplot[draw=none] {x};
\end{axis}
\end{tikzpicture}%
\end{figure}
\end{document}
Best Answer
Since you only need two different styles (as opposed to styles that differ for every label), you can use
extra x ticksfor the negative labels: