從特定的 x 軸值繪製到線交點，然後繪製到 y 軸

Question

假設繪圖並不總是直線，我建議使用該intersections庫。

\documentclass{beamer}
\beamertemplatenavigationsymbolsempty
\usepackage{verbatim}
\usepackage{tikz}
\usetikzlibrary{intersections}
\begin{document}
\begin{frame}[fragile,t]
\frametitle{}
\begin{tikzpicture}[scale=.8, transform shape]
 \pgfmathsetmacro{\incrmnty}{1.}
 \pgfmathsetmacro{\incrmntx}{2.}
 \pgfmathsetmacro{\xlab}{2006}
 \pgfmathsetmacro{\xn}{5}
 \pgfmathsetmacro{\yn}{5}
 \begin{scope}[xshift=0cm, yshift=0cm]
  \draw [thick](0,0) -- (\incrmntx*\xn+2,0);
  \node at (\incrmntx*\xn+2,\incrmnty*\yn-.4) (endx){};% to compensate for the shift of the x-axis labels, and to draw short from the end of the y-axis 
  \draw [thick](0,0) -- (0,\incrmnty*\yn);
 \end{scope}
 \begin{scope}[xshift=\incrmntx*.4cm, yshift=0cm]% to shift the x-axis labels
  \foreach \x [evaluate=\x as \aff using int(\xlab+(1*\x))]
  in {0,...,\xn}{\draw [black!20!white] (\incrmntx*\x,0) 
  node [black, xshift=0cm, yshift=-.68cm,font=\footnotesize] {\aff} -- +(-90:.2);}
  \end{scope}
  \draw[blue!40!black, line width=.4mm,name path=blue plot] (-.1*\incrmntx,1.56*\incrmnty) -- (endx.center);
  \path[overlay,name path=vert-1] (\incrmntx*\xn+.8,0) -- ++(0,10);
  \draw[blue!80!white, thick, dashed,name intersections={of=blue plot and vert-1,
  by=i1}] (\incrmntx*\xn+.8,0) |- (i1 -|0,0) node [black, left] {2011 value};
  \draw[red!40!black, line width=.4mm,name path=red plot] (-.1*\incrmntx,2.5*\incrmnty) -- (endx.center);
  \path[overlay,name path=vert-2] (\incrmntx*\xn-3.2,0) -- ++(0,10);
  \draw[red!80!white, thick, dashed,name intersections={of=red plot and vert-2,
  by=i2}] (\incrmntx*\xn-3.2,0) |- (i2 -|0,0) 
  node [black,left] {2009 value};
\end{tikzpicture}
\end{frame}
\end{document}

但是，如果您正在處理直線，calc則可以使用該庫。

\documentclass{beamer}
\beamertemplatenavigationsymbolsempty
\usepackage{verbatim}
\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}
\begin{frame}[fragile,t]
\frametitle{}
\begin{tikzpicture}[scale=.8, transform shape]
 \pgfmathsetmacro{\incrmnty}{1.}
 \pgfmathsetmacro{\incrmntx}{2.}
 \pgfmathsetmacro{\xlab}{2006}
 \pgfmathsetmacro{\xn}{5}
 \pgfmathsetmacro{\yn}{5}
 \begin{scope}[xshift=0cm, yshift=0cm]
  \draw [thick](0,0) -- (\incrmntx*\xn+2,0);
  \node at (\incrmntx*\xn+2,\incrmnty*\yn-.4) (endx){};% to compensate for the shift of the x-axis labels, and to draw short from the end of the y-axis 
  \draw [thick](0,0) -- (0,\incrmnty*\yn);
 \end{scope}
 \begin{scope}[xshift=\incrmntx*.4cm, yshift=0cm]% to shift the x-axis labels
  \foreach \x [evaluate=\x as \aff using int(\xlab+(1*\x))]
  in {0,...,\xn}{\draw [black!20!white] (\incrmntx*\x,0) 
  node [black, xshift=0cm, yshift=-.68cm,font=\footnotesize] {\aff} -- +(-90:.2);}
  \end{scope}
  \draw[blue!40!black, line width=.4mm] 
  (-.1*\incrmntx,1.56*\incrmnty) coordinate(blue-start) -- (endx.center);
  \path (intersection cs:first line={(blue-start) -- (endx.center)},
  second line={(\incrmntx*\xn+.8,0)--(\incrmntx*\xn+.8,10)}) coordinate (i1);
  \draw[blue!80!white, thick, dashed] (\incrmntx*\xn+.8,0) |- (i1 -|0,0) node [black, left] {2011 value};
  \draw[red!40!black, line width=.4mm] (-.1*\incrmntx,2.5*\incrmnty) 
  coordinate(red-start)-- (endx.center);
  \path (intersection cs:first line={(red-start) -- (endx.center)},
  second line={(\incrmntx*\xn-3.2,0)--(\incrmntx*\xn-3.2,10)}) coordinate (i2);
  \draw[red!80!white, thick, dashed] (\incrmntx*\xn-3.2,0) |- (i2 -|0,0) 
  node [black,left] {2009 value};
\end{tikzpicture}
\end{frame}
\end{document}

這會導致相同的輸出。

常見策略是確定繪圖與從指定 x 座標開始的垂直線之間的交點。在兩個例子中，這些交叉點都被稱為i1和。i2然後人們可以將它們用於

 \draw[blue!80!white, thick, dashed] (\incrmntx*\xn+.8,0) |- (i1 -|0,0) node [black, left] {2011 value};

和

  \draw[red!40!black, line width=.4mm] (-.1*\incrmntx,2.5*\incrmnty) 
  coordinate(red-start)-- (endx.center);

分別繪製垂直線和水平線，並將節點放置在它們的左側。

計算範例可以成為一種樣式。

\documentclass{beamer}
\beamertemplatenavigationsymbolsempty
\usepackage{verbatim}
\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}
\begin{frame}[fragile,t]
\frametitle{}
\begin{tikzpicture}[scale=.8, transform shape,-|/.style args={of #1 at #2}{%
insert path={(intersection cs:first line={#1},second line={(#2,0)--(#2,10)}) 
coordinate (aux) (#2,0) |- (0,0|-aux) }},vert/.style args={of #1 at #2}{%
insert path={(#2,0) 
-- (intersection cs:first line={#1},second line={(#2,0)--(#2,10)}) }}]
 \pgfmathsetmacro{\incrmnty}{1.}
 \pgfmathsetmacro{\incrmntx}{2.}
 \pgfmathsetmacro{\xlab}{2006}
 \pgfmathsetmacro{\xn}{5}
 \pgfmathsetmacro{\yn}{5}
 \begin{scope}[xshift=0cm, yshift=0cm]
  \draw [thick](0,0) -- (\incrmntx*\xn+2,0);
  \node at (\incrmntx*\xn+2,\incrmnty*\yn-.4) (endx){};% to compensate for the shift of the x-axis labels, and to draw short from the end of the y-axis 
  \draw [thick](0,0) -- (0,\incrmnty*\yn);
 \end{scope}
 \begin{scope}[xshift=\incrmntx*.4cm, yshift=0cm]% to shift the x-axis labels
  \foreach \x [evaluate=\x as \aff using int(\xlab+(1*\x))]
  in {0,...,\xn}{\draw [black!20!white] (\incrmntx*\x,0) 
  node [black, xshift=0cm, yshift=-.68cm,font=\footnotesize] {\aff} -- +(-90:.2);}
  \end{scope}
  \draw[blue!40!black, line width=.4mm] 
  (-.1*\incrmntx,1.56*\incrmnty) -- (endx.center);
  \draw[blue!80!white, thick, dashed,
  -|={of {(-.1*\incrmntx,1.56*\incrmnty)--(endx.center)} at {\incrmntx*\xn+.8}}]
  node [black, left] {2011 value};
  \draw[red!40!black, line width=.4mm] (-.1*\incrmntx,2.5*\incrmnty) -- (endx.center);  
  \draw[red!80!white, thick, dashed,
  -|={of {(-.1*\incrmntx,2.5*\incrmnty)--(endx.center)} at {\incrmntx*\xn-3.2}}]  
  node[black,left] {2009 value};
  \draw[violet!80!white, thick, dashed,
  vert={of {(-.1*\incrmntx,1.56*\incrmnty)--(endx.center)} at 
  {\incrmntx*\xn-2}}]; 
\end{tikzpicture}
\end{frame}
\end{document}

整個故事歸結為

\draw[red!80!white, thick, dashed,
  -|={of {(-.1*\incrmntx,2.5*\incrmnty)--(endx.center)} at {\incrmntx*\xn-3.2}}]  
  node[black,left] {2009 value};

vert這包含一個可以使用的附加樣式

\draw[violet!80!white, thick, dashed,
  vert={of {(-.1*\incrmntx,1.56*\incrmnty)--(endx.center)} at 
  {\incrmntx*\xn-2}}];

Answer 1