tikzpicture 的精度可以达到 4 位数字

Question

我有这个情节

\begin{tikzpicture}
     \pgfplotsset{%
        ,width=10cm
        ,legend style={font=\footnotesize}
        ,grid
        }
\begin{axis}[enlargelimits=false
            ,ymax=130
            ,ymin=0
            ,xmax=9
            ,xmin=0]
]
\addplot+[
  only marks,
]
table{tabel_3.dat};
\addlegendentry{Punctele masurate};
\addplot [blue] 
gnuplot [raw gnuplot] { 
 f(x)=a*x+b;
 a=0.0001;
 b=0.0001;
 fit f(x) 'tabel_3.dat' using 1:2 via a,b; 
 plot [x=0:12] f(x); 
 set print "parameters.dat";  
 print a, b;                  
};
\addlegendentry{\pgfplotstableread{parameters.dat}\parameters
\pgfplotstablegetelem{0}{0}\of\parameters \pgfmathsetmacro\paramA{\pgfplotsretval} 
\pgfplotstablegetelem{0}{1}\of\parameters \pgfmathsetmacro\paramB{\pgfplotsretval}
 $y=\pgfmathprintnumber{\paramA} \cdot x \pgfmathprintnumber[print sign]{\paramB} $
}    
\end{axis}
\end{tikzpicture}

使用此数据集

\begin{filecontents*}{tabel_3.dat}
X[$m$]  B[$10^{-3}T$]
1       177.12
1.5     118.30
2       88.66
2.5     70.76
3       59.03
3.5     50.73
4       44.31
4.5     39.45
5       35.42
5.5     32.25
6       29.56
6.4     27.31
7       25.30
7.5     23.64
8       22.16
\end{filecontents*}

我制作了一个拟合函数，拟合函数显示为 y=−16.32·x+ 129.59，但我需要在小数点后有 4 个数字。

Answer 1

您需要设置number format：

\begin{filecontents*}{tabel_3.dat}
X[$m$]  B[$10^{-3}T$]
1       177.12
1.5     118.30
2       88.66
2.5     70.76
3       59.03
3.5     50.73
4       44.31
4.5     39.45
5       35.42
5.5     32.25
6       29.56
6.4     27.31
7       25.30
7.5     23.64
8       22.16
\end{filecontents*}

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}


\begin{document}

\begin{tikzpicture}
   \pgfplotsset{
     /pgf/number format/precision=4, % <----
     width=10cm,
     legend style={font=\footnotesize},
     grid,
   }
\begin{axis}[
  enlargelimits=false,
  ymax=130,
  ymin=0,
  xmax=9,
  xmin=0,
]
\addplot+[
  only marks,
]
table{tabel_3.dat};
\addlegendentry{Punctele masurate};
\addplot [blue] 
gnuplot [raw gnuplot] { 
 f(x)=a*x+b;
 a=0.0001;
 b=0.0001;
 fit f(x) 'tabel_3.dat' using 1:2 via a,b; 
 plot [x=0:12] f(x); 
 set print "parameters.dat";  
 print a, b;                  
};
\addlegendentry{\pgfplotstableread{parameters.dat}\parameters
\pgfplotstablegetelem{0}{0}\of\parameters \pgfmathsetmacro\paramA{\pgfplotsretval} 
\pgfplotstablegetelem{0}{1}\of\parameters \pgfmathsetmacro\paramB{\pgfplotsretval}
 $y=\pgfmathprintnumber{\paramA} \cdot x \pgfmathprintnumber[print sign]{\paramB} $
}    
\end{axis}
\end{tikzpicture}

\end{document}

我不确定这些额外的数字意味着什么，因为您的数据只准确到第二位数字。