how to align multiple tikzpictures horizonally and vertically in one single PDF file

Question

I hope to align multiple figures plotted by tikzpictures.

As shown in the below codes, I draw eight figures, they are automatically shown in 4 rows and 2 columns, but I want them to be in 2 rows and 4 columns. Are there related methods to align them as we want, for example in 2 rows and 4 columns in this example?

Besides, I want to have them in one single PDF file and with no or narrow borders, so I use {standalone} for \documentclass.

Thank you very much

\documentclass[varwidth]{standalone}%border=3mm, 
\usepackage{tikz}
\usepackage{subfigure}
\usepackage{pgfplotstable}
\pgfplotsset{compat=newest}
\usepgfplotslibrary{units}

\begin{document}

\pgfplotsset{width=5cm,height=5cm,grid style={dashed}}
\begin{filecontents}{plottedtata.txt}
x    y1        y2        y3        y4        y5        y6        y7        y8
x    m         m         m         m         m         m         m         m
1    0.6951    0.6678    0.6753    0.9160    0.4609    0.4714    0.4735    0.1917
2    0.0680    0.8444    0.0067    0.0012    0.7702    0.0358    0.1527    0.7384
3    0.2548    0.3445    0.6022    0.4624    0.3225    0.1759    0.3411    0.2428
4    0.2240    0.7805    0.3868    0.4243    0.7847    0.7218    0.6074    0.9174
\end{filecontents}

\pgfplotstableread[
  skip first n=6, % 2+4 for filecontents header
]{plottedtata.txt}{\plottedtata}
\begin{figure}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(1), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=1,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(2), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=2,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(3), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=3,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(4), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=4,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(5), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=5,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(6), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=6,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(7), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=7,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(8), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=8,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\end{figure}
\end{document}

Answer 1

I removed the use of varwidth, I removed the use of the figure environment, and I used a stack to separate the top 4 figures from the bottom.

\documentclass{standalone}%border=3mm, 
\usepackage{tikz,stackengine}
\usepackage{subfigure}
\usepackage{pgfplotstable}
\pgfplotsset{compat=newest}
\usepgfplotslibrary{units}

\begin{document}

\pgfplotsset{width=5cm,height=5cm,grid style={dashed}}
\begin{filecontents}{plottedtata.txt}
x    y1        y2        y3        y4        y5        y6        y7        y8
x    m         m         m         m         m         m         m         m
1    0.6951    0.6678    0.6753    0.9160    0.4609    0.4714    0.4735    0.1917
2    0.0680    0.8444    0.0067    0.0012    0.7702    0.0358    0.1527    0.7384
3    0.2548    0.3445    0.6022    0.4624    0.3225    0.1759    0.3411    0.2428
4    0.2240    0.7805    0.3868    0.4243    0.7847    0.7218    0.6074    0.9174
\end{filecontents}

\pgfplotstableread[
  skip first n=6, % 2+4 for filecontents header
]{plottedtata.txt}{\plottedtata}
%\begin{figure}
\stackunder{%
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(1), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=1,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(2), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=2,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(3), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=3,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(4), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=4,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
}{
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(5), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=5,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(6), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=6,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(7), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=7,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(8), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=8,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
}
%\end{figure}
\end{document}

ADDENDUM

Per OP's follow-up comment, if one needs 3 or more rows of figures, use the syntax \Shorstack{<first row>\\<second row>\\<third row>...}, where the row separator is set via \setstackEOL{\\} (default <space>). The interrow gap can be pre-set via \setstackgap{S}{6pt}. The default alignment is centered, which can be reset with \renewcommand\stackalignment{l or c or r}.

\documentclass{standalone}%border=3mm, 
\usepackage{tikz,stackengine}
\usepackage{subfigure}
\usepackage{pgfplotstable}
\pgfplotsset{compat=newest}
\usepgfplotslibrary{units}

\begin{document}

\pgfplotsset{width=5cm,height=5cm,grid style={dashed}}
\begin{filecontents}{plottedtata.txt}
x    y1        y2        y3        y4        y5        y6        y7        y8
x    m         m         m         m         m         m         m         m
1    0.6951    0.6678    0.6753    0.9160    0.4609    0.4714    0.4735    0.1917
2    0.0680    0.8444    0.0067    0.0012    0.7702    0.0358    0.1527    0.7384
3    0.2548    0.3445    0.6022    0.4624    0.3225    0.1759    0.3411    0.2428
4    0.2240    0.7805    0.3868    0.4243    0.7847    0.7218    0.6074    0.9174
\end{filecontents}

\pgfplotstableread[
  skip first n=6, % 2+4 for filecontents header
]{plottedtata.txt}{\plottedtata}
%\begin{figure}
\setstackgap{S}{6pt}
\setstackEOL{\\}
\Shortstack{%
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(1), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=1,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(2), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=2,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(3), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=3,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\\
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(4), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=4,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(5), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=5,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(6), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=6,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\\
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(7), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=7,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}
        [color=black,grid=major,use units, y unit=m,xlabel=(8), ylabel=y,
        every major tick/.append style={thick, major tick length=3pt, black},
        every minor tick/.append style={thick, minor tick length=1.7pt, black},
        xmin=1, xmax=4, xtick={1,2,3,4}, tick align=outside, minor x tick num=1,
        ymin=0, ymax=1, minor y tick num=1]
        \addplot[draw=red,line width=1,mark=*,mark options={fill=red}] table [x index=0,y index=8,]{\plottedtata};
    \end{axis}
\end{tikzpicture}
}
%\end{figure}
\end{document}