如何在具有对数 x 轴刻度的图表上添加连接两个坐标的线？

Question

我正在尝试添加经过点 (1000,-8.5) 和 (10000,-27.79) 的线。这是我目前拥有的乳胶。

\begin{figure}[h!]
\begin{center}
\begin{tikzpicture}
\begin{axis}[
    xmode=log,
    xlabel={Frequency (Hz)},
    ylabel={Gain (db)},
    xmin=0, xmax=20000,
    ymin=-30, ymax=10,
    xtick={0,100,1000,10000},
    ytick={10,0,-10,-20,-30},
    legend pos=north west,
    ymajorgrids=true,
    grid style=dashed,
]

\addplot[
    color=blue,
    mark=square,
    only marks,
    ]
    coordinates {
    (100,-0.18)(1000,-8.5)(2000,-14.15)(4000,-19.83)(10000,-27.79)
    };

% add plot of equation going through points (1000,-8.5) and (10000,-27.79) here

\end{axis}
\end{tikzpicture}
\end{center}
\end{figure}

所有经过这两个点的方程式都无法正确显示在图中，我猜是因为对数刻度。我试过 49.37-19.29*x，但不起作用。该方程式是在计算连接两点的线之前应用 log(x) 得出的。我如何得到一条经过这些点的线？

Answer 1

怎么样

\documentclass[tikz,border=3.14mm]{standalone}

\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
    xmode=log,
    xlabel={Frequency (Hz)},
    ylabel={Gain (db)},
    xmin=0, xmax=20000,
    ymin=-30, ymax=10,
    xtick={0,100,1000,10000},
    ytick={10,0,-10,-20,-30},
    legend pos=north west,
    ymajorgrids=true,
    grid style=dashed,
    legend pos=north east
]

\addplot[
    color=blue,
    mark=square,
    only marks,
    ]
    coordinates {
    (100,-0.18)(1000,-8.5)(2000,-14.15)(4000,-19.83)(10000,-27.79)
    };
\addlegendentry{data}

\addplot[color=orange,no marks] coordinates {(1000,-8.5) (10000,-27.79)};
\addlegendentry{fit}
\end{axis}
\end{tikzpicture}
\end{document}