Ich baue ein pgfplotsund möchte Linien zwischen den Knoten und der blauen Linie zeichnen.
Ich weiß nicht, wie ich den Knoten mit der Leitung verbinde. Hoffe, jemand kann mir helfen?
\begin{tikzpicture}
\begin{axis}
[
xlabel={$x$}, ylabel={$y$}
,axis lines=middle
,xmin=0,xmax=9,ymin=0,ymax=5
,xtick={0,2,...,8}
,ytick={0,1,...,4}
,samples=41, thick
,domain=0:8
,legend pos=outer north east
]
\addplot+[no marks,blue] {0.35*x+1};
\addlegendentry{$g$}
\addplot[only marks,red] coordinates {
(2,0.8)
(3,2.4)
(4,3.2)
(5,1.8)
(6,2.8)
(7,4)
(8,2.7)
};
\addlegendentry{$gg$}
\end{axis}
\end{tikzpicture}
Antwort1
nodes near coordsBasierend auf und schlage ich Folgendes vor scatter/@pre marker code:
\documentclass[tikz, border=2mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
declare function={f(\x) = 0.35*\x + 1;},
axis lines=middle,
xlabel={$x$}, ylabel={$y$},
x label style={anchor=west, inner sep=2pt}, % <-- added
y label style={anchor=east, inner xsep=2pt}, % <-- added
hide obscured x ticks=false, % added to show the x tick at 0
hide obscured y ticks=false, % added to show the y tick at 0
xmin=0, xmax=9, ymin=0, ymax=4.9, % avoid clash with the y label
xtick distance=2, % as suggested by Stefan Pinnow
ytick distance=1, % ditto
samples=2, thick, % 2 samples are enough for a line
domain=0:8,
legend pos=outer north east,
legend style={font=\small},
]
\addplot+[no marks, blue] {f(x)};
\addlegendentry{$y = 0.35x + 1$}
\addplot[
only marks, mark=*, mark size=1pt, mark options={draw=red, fill=red},
% This is the important part:
nodes near coords={},
scatter/@pre marker code/.append code={
\draw[help lines]
(0,0)
-- (0, {f(\pgfkeysvalueof{/data point/x})-\pgfkeysvalueof{/data point/y}});
}]
coordinates {
(2,0.8)
(3,2.4)
(4,3.2)
(5,1.8)
(6,2.8)
(7,4)
(8,2.7)
};
\addlegendentry{points}
\end{axis}
\end{tikzpicture}
\end{document}
Man kann es auch mit machen scatter/position=absolute, aber es ist etwas umständlicher:
\documentclass[tikz, border=2mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
declare function={f(\x) = 0.35*\x + 1;},
axis lines=middle,
xlabel={$x$}, ylabel={$y$},
x label style={anchor=west, inner sep=2pt}, % <-- added
y label style={anchor=east, inner xsep=2pt}, % <-- added
hide obscured x ticks=false, % added to show the x tick at 0
hide obscured y ticks=false, % added to show the y tick at 0
xmin=0, xmax=9, ymin=0, ymax=4.9, % avoid clash with the y label
xtick distance=2, % as suggested by Stefan Pinnow
ytick distance=1, % ditto
samples=2, thick, % 2 samples are enough for a line
domain=0:8,
legend pos=outer north east,
legend style={font=\small},
]
\addplot+[no marks, blue] {f(x)};
\addlegendentry{$y = 0.35x + 1$}
\addplot[
only marks, forget plot,
% This is the important part:
nodes near coords={},
scatter/position=absolute,
scatter/@pre marker code/.append code={
\draw[help lines]
(\pgfkeysvalueof{/data point/x}, \pgfkeysvalueof{/data point/y})
-- (\pgfkeysvalueof{/data point/x}, {f(\pgfkeysvalueof{/data point/x})});
\path[red] plot[mark=*, mark size=1pt, only marks]
coordinates {(\pgfkeysvalueof{/data point/x},
\pgfkeysvalueof{/data point/y})};
}]
coordinates {
(2,0.8)
(3,2.4)
(4,3.2)
(5,1.8)
(6,2.8)
(7,4)
(8,2.7)
};
\addlegendimage{
legend image code/.code={
\draw[red]
plot[only marks, mark=*, mark size=1pt] coordinates { (0.3cm,0cm) };
},
}
\addlegendentry{points}
\end{axis}
\end{tikzpicture}
\end{document}
Gleiche Ausgabe wie oben.
Antwort2
Dies ist eine verbesserte Antwort (die für einen Kommentar zu lang ist) auf die (ebenfalls) großartige Idee vonVenez(+1) Verwenden von a tableanstelle von coordinates. Das macht das Leben viel einfacher :)
% used PGFPlots v1.16
\documentclass[border=5pt]{standalone}
\usepackage{pgfplots}
% create an empty plot mark
% (which is needed later)
\pgfdeclareplotmark{noMark}{}
\begin{document}
\begin{tikzpicture}[
declare function={foo(\x) = 0.35 * \x + 1;}
]
\begin{axis}[
xmin=0,xmax=9,ymin=0,ymax=5,
% (replaced `[x|y]tick`s)
xtick distance=2,
ytick distance=1,
xlabel={$x$},
ylabel={$y$},
axis lines=middle,
hide obscured x ticks=false,
hide obscured y ticks=false,
samples=2, % <-- (more than 2 samples are not needed for a straight line)
domain=0:8,
legend pos=outer north east,
thick,
]
\addplot[blue] {foo(x)};
\addlegendentry{$g$}
% add a custom legend entry to imitate a "normal" mark plot
\addlegendimage{red,only marks,mark=*}
\addlegendentry{$gg$}
% since this is the last plot and no more `\addlegendentry` is given
% it doesn't show up in the legend
\addplot+ [
red,
only marks,
% don't show the normal mark ...
mark=noMark,
error bars/.cd,
y dir=both,
y explicit,
% ... show the mark at the error (position)
error mark=*,
% replaced `coordinates` by a table which allows to calculate the
% appropriate error position easily
] table [
x=x,
y expr={foo(\thisrow{x})},
y error plus expr={\thisrow{y} - foo(\thisrow{x})},
] {
x y
2 0.8
3 2.4
4 3.2
5 1.8
6 2.8
7 4.0
8 2.7
};
\end{axis}
\end{tikzpicture}
\end{document}
Antwort3
Ich glaube, mein Versuch ist ein bisschen zu viel Schummelei, aber er funktioniert.
\documentclass[tikz]{standalone}
\usepackage{pgfplots}
\begin{document}
\pgfdeclareplotmark{noMark}{}
\begin{tikzpicture}[
declare function={foo(\x) = 0.35 * \x + 1;}
]
\begin{axis}
[
xlabel={$x$}, ylabel={$y$}
,axis lines=middle
,xmin=0,xmax=9,ymin=0,ymax=5
,xtick={0,2,...,8}
,ytick={0,1,...,4}
,samples=41, thick
,domain=0:8
,legend pos=outer north east
]
\addplot[blue] {foo(x)};
\addlegendentry{$g$}
\addlegendimage{red,only marks,mark=*}
\addlegendentry{$gg$}
%
\addplot+ [
red,
only marks,
mark=noMark,
error bars/.cd,
y dir=both,
y explicit,
error mark=*,
] coordinates {
(2,{foo(2)}) += (0,{0.8-foo(2)})
(3,{foo(3)}) += (0,{2.4-foo(3)})
(4,{foo(4)}) += (0,{3.2-foo(4)})
(5,{foo(5)}) += (0,{1.8-foo(5)})
(6,{foo(6)}) += (0,{2.8-foo(6)})
(7,{foo(7)}) += (0,{4.0-foo(7)})
(8,{foo(8)}) += (0,{2.7-foo(8)})
};
\end{axis}
\end{tikzpicture}
\end{document}
