請建議如何使用以下程式碼中的 X 和 Y 列的值來擬合 a 和 b
\documentclass{article}
\usepackage{gnuplot-lua-tikz}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{\gpbboxborder}
\begin{document}
\begin{tikzpicture}[gnuplot]
\begin{axis}[
width=10cm,
xlabel={something},
ylabel={something},
]
\addplot [blue,only marks] table [x=X, y=Y] {
X Y
145444 3746643.308
145250 3972396.385
145183 5026818
145449 8220037.462
145355 7696519.385
145347 7952214.231
145394 5869103.66
145421 7268796.583
145249 8472536.083
145237 9305086.167
145358 5155636.25
145416 6077647.583
145337 5861633.167
145384 4426391.667
145229 4101591.378
145392 4570673.462
145271 6972571.692
145287 6527322.308
145319 4211914.846
145321 4735368.385
145411 7849477.75
145349 8152333.083
145233 4891463
145261 5013476.583
145424 4030219.154
145381 4528078.154
145326 5445707.231
145413 5461362.231
145311 5619711.846
145409 9969929.462
145248 5306496.923
145270 7.53E+06
145281 4478472.083
145341 5173546.667
};
{f(x)};
\addplot [thick,red,dashed,id=test] gnuplot [raw gnuplot] {
X Y
145444 3746643.308
145250 3972396.385
145183 5026818
145449 8220037.462
145355 7696519.385
145347 7952214.231
145394 5869103.66
145421 7268796.583
145249 8472536.083
145237 9305086.167
145358 5155636.25
145416 6077647.583
145337 5861633.167
145384 4426391.667
145229 4101591.378
145392 4570673.462
145271 6972571.692
145287 6527322.308
145319 4211914.846
145321 4735368.385
145411 7849477.75
145349 8152333.083
145233 4891463
145261 5013476.583
145424 4030219.154
145381 4528078.154
145326 5445707.231
145413 5461362.231
145311 5619711.846
145409 9969929.462
145248 5306496.923
145270 7.53E+06
145281 4478472.083
145341 5173546.667
f(x) = a*x + b;
a = 2000;
b = -3e8;
% fit a and b by `using' columns 1 and 2 of 'data.txt'
fit f(x) 'X Y' using 1:2 via a, b;
straight line
set samples 2;
plot [x=145183:145449] f(x);
};
\end{axis}
\end{tikzpicture}
\end{document}
循環可能是一個解決方案，但無法弄清楚如何運行它。
無法在序言中定義 .text 檔案中的值，因為需要在文件中新增多個繪圖。
答案1
pgfplots以及pgfplotstable可用於線性迴歸。迴歸係數的值將儲存在 \pgfplotstableregressiona和中\pgfplotstableregressionb。
請參閱下面給出的程式碼。請注意，\res在應用迴歸之前，資料已排序並儲存。
\documentclass[border=3mm]{standalone}
\usepackage{pgfplots}
\usepackage{pgfplotstable}
\pgfplotsset{compat=1.16}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
xlabel={something},
ylabel={something},
]
\pgfplotstablesort{\res}{
X Y
145444 3746643.308
145250 3972396.385
145183 5026818
145449 8220037.462
145355 7696519.385
145347 7952214.231
145394 5869103.66
145421 7268796.583
145249 8472536.083
145237 9305086.167
145358 5155636.25
145416 6077647.583
145337 5861633.167
145384 4426391.667
145229 4101591.378
145392 4570673.462
145271 6972571.692
145287 6527322.308
145319 4211914.846
145321 4735368.385
145411 7849477.75
145349 8152333.083
145233 4891463
145261 5013476.583
145424 4030219.154
145381 4528078.154
145326 5445707.231
145413 5461362.231
145311 5619711.846
145409 9969929.462
145248 5306496.923
145270 7.53E+06
145281 4478472.083
145341 5173546.667
};
{f(x)};
\addplot [blue,only marks] table [sort, sort key=X, x=X, y=Y] {\res};
\addplot [dashed,red,thick] table [x=X, y={create col/linear regression={y=Y}}] {\res};
\addlegendentry {data}
\addlegendentry{%
$\pgfmathprintnumber{\pgfplotstableregressiona} \times x
\pgfmathprintnumber[print sign]{\pgfplotstableregressionb}$}
\end{axis}
\end{tikzpicture}
\end{document}