\documentclass[a4paper,12pt]{article}
\usepackage{graphicx}
\usepackage{amsthm}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{pgfplots}
\usepackage{mathrsfs}
\usepackage{fancybox}
\usepackage{fancyhdr}
\usepackage[all]{xy}
\usepackage{setspace}
\usepackage{makeidx}
\makeindex
\RequirePackage{hyperref}
\usepackage{xepersian}
\settextfont[ItalicFont={XB Zar Oblique}]{XB Niloofar}
\begin{document}
 \begin{tikzpicture}
\begin{axis}[axis lines=middle,xlabel=$x$,ymin=-2,ymax=2,xmin=-2,xmax=5,minor y tick num=5,grid=major,minor x tick num=5]
\addplot{x-\lfloor x \rfloor };
\end{axis}
\end{tikzpicture}
\end{document}