填充曲线上方的区域

Question

我正在尝试填充曲线上方和直线下方的区域，但曲线有问题，有一块区域无法填充！谢谢！

\begin{tikzpicture}
\draw[thick,<->](0,6.5) node[above]{$p$}--(0,0)--(6.5,0) node[right]{$Q$};
\draw(0,6)--(5,0) node[above right]{$D(p_t)$};
\draw(0,0) ..controls (4.3,1.5) and (6,6) .. (6,6) node[right]{$C(Q_t)$};
\draw[dashed] (0,2.05) node[left]{$p_t$}--(3.3,2.05)--(3.3,0)node[below]{$Q_t$};
\path[pattern=north east lines] (0,2.05)--(3.3,2.05)--(0,6);
\path[pattern=north east lines] (0,2.05)--(3.3,2.05)--(0,0);
\end{tikzpicture}

Answer 1

我不确定您想要为图表的哪一部分添加阴影。一种直接的方法是使用\clip：

\documentclass[border=10pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{patterns}

\begin{document}
\begin{tikzpicture}

\draw[thick, <->] 
    (0,6.5) node[above] {$p$} --
    (0,0) --
    (6.5,0) node[right] {$Q$};
\draw
    (0,6) -- 
    (5,0) node[above right]{$D(p_t)$};
\draw
    (0,0) .. controls (4.3,1.5) and (6,6) .. 
    (6,6) node[right] {$C(Q_t)$};    

\begin{scope}
    \clip
        (0,0) .. controls (4.3,1.5) and (6,6) .. 
        (6,6) -- (0,6) -- cycle;    
    \path[pattern=north east lines] 
        (0,0) -- (5,0) -- (0,6) -- cycle;
\end{scope}

\draw[dashed]
    (0,2.05) node[left] {$p_t$} --
    (3.3,2.05) -- 
    (3.3,0) node[below] {$Q_t$};

\end{tikzpicture}
\end{document}

为了获得更大的灵活性并减少路径的重复使用，您还可以使用fillbetween提供的库pgfplots（也会加载tikz）：

\documentclass[border=10pt]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usetikzlibrary{patterns, fillbetween}

\begin{document}
\begin{tikzpicture}

\draw[thick, <->] 
    (0,6.5) node[above] {$p$} --
    (0,0) --
    (6.5,0) node[right] {$Q$};
\draw 
    (0,6) -- 
    (5,0) node[above right]{$D(p_t)$};
\draw[name path=curve]
    (0,0) .. controls (4.3,1.5) and (6,6) .. 
    (6,6) node[right] {$C(Q_t)$};
\draw[dashed, name path=segment] 
    (0,2.05) node[left] {$p_t$} --
    (3.3,2.05) -- 
    (3.3,0) node[below] {$Q_t$};
\path[pattern=north east lines] 
    (0,2.05) -- (3.3,2.05) -- (0,6) -- cycle;

\fill[
    pattern=north west lines, 
    intersection segments={
        of={curve and segment}, 
        sequence={L1 -- R1[reverse]}
    }
] -- cycle;

\end{tikzpicture}
\end{document}