diagrams

\documentclass{article}
\usepackage[english,russian]{babel}
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{width = 15 cm, compat = 1.3}


\begin{document}
\begin{tikzpicture}
\begin{axis}[
title = Simple function 1,
xmin = -30,
xmax = 30,
ymin = -30,
ymax = 30,
grid = major,
legend style = {at ={ (0.5, -0.1)}, anchor = north,
legend columns = -1;}
]
\addplot[domain=-10:10, red, line width = 2pt]{x^2};
\addplot+[domain=-10:10, blue, line width = 2pt]{-x^2};
\addplot[domain=-10:10, magenta, line width = 1pt]{x^3};
\addplot[domain=-10:10, orange, line width = 1pt]{-x^3};
\addplot[domain=-30:30, dashed]{x}; %solid - сплошная, dotted - в виде точек
\addplot[domain=-30:30, dotted]{-x};
\legend{$x^2$, $-x^2$, $x^3$, $-x^3$, $x$, $-x$};
\end{axis}
\end{tikzpicture}

\begin{tikzpicture}
\begin{axis}[
title = simple function 2,
axis lines = middle,
samples=500,
xlabel = Ox,
ylabel = Oy,
xmin = -10,
xmax = 10,
ymin = -10,
ymax = 10,
minor tick num = 1,
grid = major,
grid style = dotted,
restrict y to domain=-10:10
]
\addplot[domain = -10:10, blue] {1/x};
\addplot[domain = -10:10, red, line width = 2 pt] {-1/x};
\end{axis}
\end{tikzpicture}

\begin{tikzpicture}
\begin{axis}[
title = Temperature dependance of Time,
xlabel = {Temperature, C},
ylabel = {Time, sec},
xmin = 0, xmax =  100, ymin = 0, ymax = 60,
xtick = {0, 20, 40, 60, 80, 100}, %(0, 20, ..., 100)
ytick = {0, 20, 40, 60},
minor tick num = 2,
grid = both, %minor, none
grid style = dashed,
legend pos =north west
]
\addplot[const plot, blue, mark = square, mark size = 3 pt] %smooth
coordinates
 {(0.0) (10, 8.7) (9, 7) (1.2, 2.3) (4, 5) (100, 55) (90, 2) (15, 45)};
 \legend{water}
\end{axis}
\end{tikzpicture}

\begin{tikzpicture}
\begin{axis}[
title = Средний балл ЕГЭ,
ybar,
bar width = 23 pt,
xlabel = years,
ylabel = points,
ymin = 0,
ymax = 100,
xtick = {2013, 2014, 2015},
ytick = {0, 20, ..., 100},
minor tick num = 1,
grid = major,
grid style = dashed,
legend style={at={(0.5, -0.18)},anchor = south, legend columns = -1},
]
\addplot coordinates {(2013, 37.5) (2014, 60) (2015, 78)};
\addplot coordinates {(2013, 45) (2014, 50) (2015, 88)};
\legend{Саратов, Москва};
\end{axis}
\end{tikzpicture}

\end{document}