我对曲线之间填充区域的图例有疑问。我想要一个带有小方块的图例项，它表示函数之间的填充。当我在 /addplot 中使用“区域图例”时，图例项显示为虚线而不是小方块。
\begin{figure}[H]
\centering
\begin{tikzpicture}[scale = 0.91]
\begin{axis}[
scale only axis,
xlabel={Napätie \(U_{DS} [V]\)},
ylabel={Prúd \(I_D [A]\)},
xmin=0, xmax=20,
ymin=0, ymax=0.8,
ymajorgrids=true,
xmajorgrids=true,
legend style={at={(0.5,0.98)},anchor=north}
]
\addplot[line width=1.5pt,solid,color=blue]
coordinates {(0,0)(1.67,0.16)(1.8,0.18)(2.2,0.2)(17.7,0.22)(18.5,0.25)(19,0.3)(19.8,0.8)};
\addlegendentry{\(U_{GS}\) = 2 V}
\addplot[line width=1.5pt,solid,color=red]
coordinates {(0,0)(2.2,0.34)(2.35,0.37)(2.9,0.4)(18,0.42)(18.2,0.43)(18.7,0.445)(19,0.48)(19.7,0.8)};
\addlegendentry{\(U_{GS}\) = 2.2 V}
\addplot[line width=1.5pt,solid,color=green]
coordinates {(0,0)(2.6,0.56)(2.8,0.58)(3.2,0.6)(18,0.62)(18.4,0.64)(18.6,0.65)(19,0.7)(19.6,0.8)};
\addlegendentry{\(U_{GS}\) = 2.4 V}
\addplot[name path=B, line width=1pt,solid,color=black, smooth,dashed]
coordinates {(0,0)(2.2,0.2)(2.9,0.4)(3.2,0.6)(3.5,0.8)};
\addplot[name path=C, line width=1pt,solid,color=black, smooth,dashed]
coordinates {(16.5,0)(17.7,0.22)(18,0.42)(18,0.62)(18.2,0.8)};
\addplot[draw=none, name path=A, line width=1pt,solid]
coordinates {(0,0)(0.01,0.8)};
\addplot[draw=none, name path=D, line width=1pt,solid]
coordinates {(19.9,0)(20,0.8)};
\addplot[pattern=north west lines, pattern color=apricot, area legend] fill between[of=A and B];
\addlegendentry{Saturation region}
\addplot[pattern=north west lines, pattern color=babyblueeyes] fill between[of=B and C];
\addplot[pattern=north west lines, pattern color=babypink] fill between[of=C and D];
\end{axis}
\end{tikzpicture}
\caption{Výstupná charakteristika MOSFET tranzistora}
\label{fig:MOS_output}
\结束{图}
答案1
你忘了几个forget plots（并且还要提供 MWE，所以我不得不替换一些颜色）。forget plot可以用来忽略图例中的相应情节。
\documentclass[tikz,border=3mm,dvipsnames]{standalone}
\usepackage{pgfplots}
\usetikzlibrary{patterns}
\usepgfplotslibrary{fillbetween}
\pgfplotsset{compat=1.17}
\begin{document}
\begin{tikzpicture}[scale = 0.91]
\begin{axis}[
scale only axis,
xlabel={Nap\"atie \(U_{DS} [V]\)},
ylabel={Pr\'ud \(I_D [A]\)},
xmin=0, xmax=20,
ymin=0, ymax=0.8,
ymajorgrids=true,
xmajorgrids=true,
legend style={at={(0.5,0.98)},anchor=north}
]
\addplot[line width=1.5pt,solid,color=blue]
coordinates {(0,0)(1.67,0.16)(1.8,0.18)(2.2,0.2)(17.7,0.22)(18.5,0.25)(19,0.3)(19.8,0.8)};
\addlegendentry{\(U_{GS}\) = 2 V}
\addplot[line width=1.5pt,solid,color=red]
coordinates {(0,0)(2.2,0.34)(2.35,0.37)(2.9,0.4)(18,0.42)(18.2,0.43)(18.7,0.445)(19,0.48)(19.7,0.8)};
\addlegendentry{\(U_{GS}\) = 2.2 V}
\addplot[line width=1.5pt,solid,color=green]
coordinates {(0,0)(2.6,0.56)(2.8,0.58)(3.2,0.6)(18,0.62)(18.4,0.64)(18.6,0.65)(19,0.7)(19.6,0.8)};
\addlegendentry{\(U_{GS}\) = 2.4 V}
\addplot[name path=B, line width=1pt,solid,color=black, smooth,dashed,forget plot]
coordinates {(0,0)(2.2,0.2)(2.9,0.4)(3.2,0.6)(3.5,0.8)};
\addplot[name path=C, line width=1pt,solid,color=black, smooth,dashed,forget plot]
coordinates {(16.5,0)(17.7,0.22)(18,0.42)(18,0.62)(18.2,0.8)};
\addplot[draw=none, name path=A, line width=1pt,solid,forget plot]
coordinates {(0,0)(0.01,0.8)};
\addplot[draw=none, name path=D, line width=1pt,solid,forget plot]
coordinates {(19.9,0)(20,0.8)};
\addplot[pattern=north west lines, pattern color=Apricot, area legend] fill between[of=A and B];
\addlegendentry{Saturation region}
\addplot[pattern=north west lines, pattern color=blue!20] fill between[of=B and C];
\addplot[pattern=north west lines, pattern color=pink] fill between[of=C and D];
\end{axis}
\end{tikzpicture}
\end{document}
