Prima di ogni figura ricordare di mettere
\documentclass[usenames,dvipsnames]{article}
\usepackage{pgfplots}
Figura
Codice della figura
\begin{tikzpicture}
\begin{axis}[
axis equal image,
axis x line=center,
axis y line=center,
xmin = -3.5,
xmax = 3.5,
ymin = -3.5,
ymax = 3.5,
xlabel = {$x$},
ylabel = {$y$},
ylabel style={anchor=north east},
extra x ticks = {0},
extra x tick label = {$\hspace{0.4cm}0$},
xtick={-4,-3,...,4},
ytick={-4,-3,...,4},
yticklabel style={right,xshift={1ex}},
]
\foreach \x in {-4,-3,...,4} {
\addplot[very thick,blue] coordinates {(\x,\x) (1+\x,\x)};
\addplot[only marks,mark=*,blue] coordinates {(\x,\x)};
\addplot[only marks,mark=*,blue,mark options={fill=white},thick] coordinates {(1+\x,\x)};
}
\addplot[blue,no marks] coordinates {(-2,2)} node {$y=\lfloor x \rfloor$};
\end{axis}
\end{tikzpicture}