\documentclass[border=10pt]{standalone}
\usepackage{siunitx}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usepackage{pgfplotstable}
\usepackage{filecontents}
\begin{filecontents*}{myData.dat}
X     Y
8.900        17.698
11.700        17.698
13.200        27.365
13.400        27.365
14.000        37.031
14.200        37.031
14.000        27.365
10.700        17.698
21.671        66.030
23.487        75.696
20.902        56.364
16.507        37.031
\end{filecontents*}
\begin{document}
\begin{tikzpicture}
\pgfplotsset{
width=10cm,
legend style={font=\scriptsize}
}
\begin{axis}[%
xlabel=$x$,
ylabel=$y$,
ymin=0,
xmin=0,
scaled y ticks=base 10:0,
legend cell align = left,
legend pos = north west
]
\addplot[only marks] table {mydata.dat};
\addlegendentry{scatter plot};
\addplot+[no markers,red] table [y={create col/linear regression={y=Y}}]{myData.dat};
\addlegendentry{%
Linear regression:  $y=\pgfmathprintnumber{\pgfplotstableregressiona} x
\pgfmathprintnumber[print sign]{\pgfplotstableregressionb}$};
% polynomial fit
\addplot [no markers, blue] gnuplot [raw gnuplot] { % allows arbitrary gnuplot commands
f(x) = a*x**2+b*x+c;     % Define the function to fit
a=10;b=10; c=10;         % Set reasonable starting values here
fit f(x) 'myData.dat' u 1:2 via a,b,c; % Select the file, starts at col 1 and two variables
plot [x=0:28] f(x);    % Specify the range to plot
set print "parameters.dat";  % Open a file to save the parameters
print a, b, c;                  % Write the parameters to file
};
\addlegendentry{\pgfplotstableread{parameters.dat}\parameters % Open the file Gnuplot wrote
\pgfplotstablegetelem{0}{0}\of\parameters \pgfmathsetmacro\paramA{\pgfplotsretval} % Get first element, save into \paramA
\pgfplotstablegetelem{0}{1}\of\parameters \pgfmathsetmacro\paramB{\pgfplotsretval}
\pgfplotstablegetelem{0}{2}\of\parameters \pgfmathsetmacro\paramC{\pgfplotsretval}
polynomial:$y=\pgfmathprintnumber{\paramA} x^2 \pgfmathprintnumber[print sign]{\paramB} x \pgfmathprintnumber[print sign]{\paramC}$
}
\end{axis}
\end{tikzpicture}
\end{document}

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8Â¥: Originally posted by zhangzhiguang at 2014-06-28 11:31:55
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