pgfplotspgfplotstabletikz-pgf
I am loading two curves from a file and plot them with \addplot table [...] {the table.txt}; I have managed to fill the area under a single curve, but I want the minimum of the two curves filled. What is the preferred way to accomplish this using tikz and pgfplots? The image shows an example of the desired result.
Thanks for any help.
Here's a macro that generates a new table \interpolated that places points on your original data at every intersection with a certain y-value. You call it using \findintersections{<table macro}{<value>}.
To plot the area above the line, you would then use \addplot[fill,gray!20!white,no markers,line width=2pt] table [y=above line] {\interpolated};, or ...table [y=below line] for the area below the line.
In order to close the area properly in case your plot stops or begins above the cutoff line, you should add |- (current plot begin) at the end of the plot command.
\documentclass{article}
\usepackage{pgfplots}
\usepackage{pgfplotstable}
\usepackage{filecontents}
\usetikzlibrary{calc}
\begin{filecontents}{data.dat}
0 0.2
1 0.217
2 0.255
3 0.288
6 0.58
7 0.91
8 1.02
10 1.05
12 0.92
13 0.78
15 0.56
17 1.1
\end{filecontents}
\pgfplotstableread{data.dat}\data
\newcommand\findintersections[2]{
\def\prevcell{#1}
\pgfplotstableforeachcolumnelement{1}\of#2\as\cell{%
\pgfmathparse{!or(
and(
\prevcell>#1,\cell>#1
),
and(
\prevcell<#1,\cell<#1
)
)}
\ifnum\pgfmathresult=1
\pgfplotstablegetelem{\pgfplotstablerow}{0}\of{\data} \let\xb=\pgfplotsretval
\pgfplotstablegetelem{\pgfplotstablerow}{1}\of{\data} \let\yb=\pgfplotsretval
\pgfmathtruncatemacro\previousrow{ifthenelse(\pgfplotstablerow>0,\pgfplotstablerow-1,0)}
\pgfplotstablegetelem{\previousrow}{0}\of{\data} \let\xa=\pgfplotsretval
\pgfplotstablegetelem{\previousrow}{1}\of{\data} \let\ya=\pgfplotsretval
\pgfmathsetmacro\newx{
\xa+(\ya-#1)/(ifthenelse(\yb==\ya,1,\ya-\yb) )*(\xb-\xa) }
\edef\test{\noexpand\pgfplotstableread[col sep=comma,row sep=crcr,header=has colnames]{
0,1\noexpand\\
\newx,#1\noexpand\\
}\noexpand\newrow}
\test
\pgfplotstablevertcat\interpolated{\newrow}
\fi
\let\prevcell=\cell
}
\pgfplotstablevertcat\interpolated{#2}
\pgfplotstablesort[sort cmp={float <}]\interpolated{\interpolated}
\pgfplotstableset{
create on use/above line/.style={
create col/expr={max(\thisrow{1},#1)}
},
create on use/below line/.style={
create col/expr={min(\thisrow{1},#1)}
},
}
}
\begin{document}
\pgfplotsset{compat=newest} % For nicer label placement
\findintersections{0.9}{\data}
\begin{tikzpicture}
\begin{axis}[
xlabel=Time of day,
ylabel=Volume,
ytick=\empty,
axis x line=bottom,
axis y line=left,
enlargelimits=true
]
\addplot[fill,gray!20!white,no markers,line width=2pt] table [y=above line] {\interpolated} |- (current plot begin);
\addplot[fill,yellow!20!white,no markers,line width=2pt] table [y=below line] {\interpolated} |- (current plot begin);
\addplot[orange,no markers,line width=2pt,domain=-1:20] {0.9};
\addplot[blue,line width=2pt,mark=*] table {\data};
\end{axis}
\end{tikzpicture}
\end{document}
I think the easiest way to do this is to use two \addplot commands for the function, with different domains. To fill the area above the right side of the plot, you can append |- ({rel axis cs:0,1}-|{current plot begin}) after the \addplot command:
\documentclass[border=5mm]{standalone}
\usepackage{pgfplots}
\usetikzlibrary{patterns}
\begin{document}
\begin{tikzpicture}
\begin{axis}[xmin=0,xmax=5,ymin=0,ymax=5]
\addplot [domain=0:2,samples=100, pattern=north east lines]
{(x - 2)^2/(7*x) + 1} |- (current plot begin) ;
\addplot [domain=2:5,samples=100, pattern=north west lines]
{(x - 2)^2/(7*x) + 1} |- ({rel axis cs:0,1}-|{current plot begin}) ;
\addplot [color=blue, thick, dashed] plot coordinates {(2,0) (2,5)} ;
\end{axis}
\end{tikzpicture}
\end{document}
Best Answer
This can be done by the
fillbetweenlibrary which is shipped withpgfplotsversion 1.10:The idea is to use the new
intersection segmentspath instructions provided byfillbetween. It accepts to labelled paths on input and asequenceof intersection segments. Currently, the "minimum" needs to be provided manually. In your case, you need to use the first (0th) segment of the first (A) curve (A0), then the second (1st) of the second curve (B) which isB1, followed by the third (2rd) segment of the first curve which isA2. The other statements specify the bottom line of the filled region. The layering instructionsset layersand\pgfonlayermake sure that the stuff appears behind the labelled input paths.Note that version 1.10 is very young at the time of this writing - you might need a software upgrade.