我想为我的两个图（红色和黑色）添加图例，但图例似乎存在一些缩放问题。我认为这可能是由于移位和域的变化造成的，但我不确定！
\newcommand{\vasymptote}[2][]{
\draw [color=gray,densely dashed,#1] ({rel axis cs:0,0} -| {axis cs:#2,0}) -- ({rel axis cs:0,1} -| {axis cs:#2,0});
}
\begin{tikzpicture}
\begin{axis}[
xlabel={Distance (m)},
ylabel={Moment (kNm)}, xmin=0,xmax=60,width=29.7cm,height=21cm, title={Moment Envelopes}, grid=both, y dir=reverse, ytick={-5500,-5000,...,1500},]
% Axis
\addplot[gray,thick,domain=0:60,shift={(0,0)},forget plot] {0}; %x axis
\vasymptote {7.5};
\vasymptote {22.5};
\vasymptote {37.5};
\vasymptote {52.5};
% 1.2G + 1.5 Q
\addplot[black,smooth,domain=0:7.5,shift={(0,0)}, line legend] {-46.61*x^2 - 349.6*x}; % A
\addplot[black,smooth,domain=0:15,shift={(75,0)}, forget plot] {-54.22*x^2 + 829.29*x - 2206}; % B
\addplot[black,smooth,domain=0:15,shift={(225,0)}, forget plot] {-54.22*x^2 + 813.22*x - 2020}; % C
\addplot[black,smooth,domain=0:15,shift={(375,0)}, forget plot] {-54.22*x^2 + 797.16*x - 1965}; % D
\addplot[black,smooth,domain=0:7.5,shift={(525,0)}, forget plot] {-46.61*(7.5-x)^2 - 349.6*(7.5-x)}; % E
\addlegendentry{Black Line}
% G + 0.3 Q
\addplot[red,smooth,domain=0:7.5,shift={(0,0)}, line legend] {-29.36*x^2 - 220.25*x}; % A
\addplot[red,smooth,domain=0:15,shift={(75,0)}, forget plot] {-36.6*x^2 + 559.77*x - 1489.05}; % B
\addplot[red,smooth,domain=0:15,shift={(225,0)}, forget plot] {-36.6*x^2 + 548.92*x - 1363.5}; % C
\addplot[red,smooth,domain=0:15,shift={(375,0)}, forget plot] {-36.6*x^2 + 538.68*x - 1326.38}; % D
\addplot[red,smooth,domain=0:7.5,shift={(525,0)}, forget plot] {-29.36*(7.5-x)^2 - 220.25*(7.5-x)}; % E
\addlegendentry{Red Line}
\end{axis}
\end{tikzpicture}
取消反转 y 轴会导致图例尺寸减小，但不能解决问题。
任何帮助都将非常有帮助，谢谢！
答案1
是的，这是由命令引起的shift。您不应该使用常规的 TikZ 转换命令（如shift或scale）来更改绘图，因为它们在“纸张域”中运行，而您应该在“数据域”中工作。因此，如果您想将绘图向右移动 7.5 个“数据单位”，您可以更改函数（\addplot [...] { -36.6*(x-7.5)^2 + 559.77*(x-7.5) - 1489.05 };），也可以使用坐标过滤器：
x filter/.code=\pgfmathparse{\pgfmathresult+7.5}
将会给图中所有的 x 坐标添加 7.5。
\documentclass{standalone}
\usepackage{pgfplots}
\begin{document}
\newcommand{\vasymptote}[2][]{
\draw [color=gray,densely dashed,#1] ({rel axis cs:0,0} -| {axis cs:#2,0}) -- ({rel axis cs:0,1} -| {axis cs:#2,0});
}
\begin{tikzpicture}
\begin{axis}[
xlabel={Distance (m)},
ylabel={Moment (kNm)}, xmin=0,xmax=60,width=29.7cm,height=21cm, title={Moment Envelopes}, grid=both, y dir=reverse, ytick={-5500,-5000,...,1500},]
% Axis
\addplot[gray,thick,domain=0:60,shift={(0,0)},forget plot] {0}; %x axis
\vasymptote {7.5};
\vasymptote {22.5};
\vasymptote {37.5};
\vasymptote {52.5};
% 1.2G + 1.5 Q
\addplot[black,smooth,domain=0:7.5, line legend] {-46.61*x^2 - 349.6*x}; % A
\addplot[black,smooth,domain=0:15, x filter/.code=\pgfmathparse{\pgfmathresult+7.5}, forget plot] {-54.22*x^2 + 829.29*x - 2206}; % B
\addplot[black,smooth,domain=0:15, x filter/.code=\pgfmathparse{\pgfmathresult+22.5}, forget plot] {-54.22*x^2 + 813.22*x - 2020}; % C
\addplot[black,smooth,domain=0:15, x filter/.code=\pgfmathparse{\pgfmathresult+37.5},, forget plot] {-54.22*x^2 + 797.16*x - 1965}; % D
\addplot[black,smooth,domain=0:7.5,x filter/.code=\pgfmathparse{\pgfmathresult+52.5}, forget plot] {-46.61*(7.5-x)^2 - 349.6*(7.5-x)}; % E
\addlegendentry{Black Line}
% G + 0.3 Q
\addplot[red,smooth,domain=0:7.5, line legend] {-29.36*x^2 - 220.25*x}; % A
\addplot[red,smooth,domain=0:15, x filter/.code=\pgfmathparse{\pgfmathresult+7.5}, forget plot] {-36.6*x^2 + 559.77*x - 1489.05}; % B
\addplot[red,smooth,domain=0:15, x filter/.code=\pgfmathparse{\pgfmathresult+22.5}, forget plot] {-36.6*x^2 + 548.92*x - 1363.5}; % C
\addplot[red,smooth,domain=0:15, x filter/.code=\pgfmathparse{\pgfmathresult+37.5}, forget plot] {-36.6*x^2 + 538.68*x - 1326.38}; % D
\addplot[red,smooth,domain=0:7.5, x filter/.code=\pgfmathparse{\pgfmathresult+52.5}, forget plot] {-29.36*(7.5-x)^2 - 220.25*(7.5-x)}; % E
\addlegendentry{Red Line}
\end{axis}
\end{tikzpicture}
\end{document}