Is it possible to have a smaller plot embedded into one of the plots of a groupplot? What I would like to achieve is like a magnified region of the lower plot, it should display two rectangles, one smaller that indicates the region magnified, and another a little bigger where the magnification is visible. I've tried to use \usetikzlibrary{spy}, but it does just a simple zoom of a region. I would like to have the control of the ytick parameter of the magnified region, in order to "stretch" potential curves that appears overlapped. The graphical structure I would like to get is the following:
And here a dummy MWE to try out a possible solution:
\documentclass{article}
\usepackage[dvipsnames]{xcolor}
\usepackage{pgf,pgfplots,pgfplotstable}
\pgfplotsset{compat=newest}
\usepgfplotslibrary{colormaps}
\usepgfplotslibrary{groupplots}
%\usetikzlibrary{spy}
\begin{filecontents}{data1.dat}
t1 a1 t2 a2 t3 a3
0.142 1.000 0.154 1.000 0.139 0.995
0.284 1.000 0.308 1.000 0.279 0.990
0.426 1.000 0.461 1.000 0.418 0.989
0.569 1.000 0.615 1.000 0.558 0.989
0.711 1.000 0.769 1.000 0.697 0.989
0.853 1.000 0.923 1.000 0.836 0.989
0.995 1.000 1.077 1.000 0.976 0.989
1.137 1.000 1.230 1.000 1.115 0.989
1.279 1.000 1.384 1.000 1.255 0.989
1.422 0.995 1.538 1.000 1.394 0.986
1.564 0.990 1.692 1.000 1.534 0.981
\end{filecontents}
\begin{filecontents}{data2.dat}
t1 a1 t4 a4 t3 a3
3.554 0.920 3.845 0.950 3.485 0.913
3.696 0.915 3.999 0.945 3.625 0.908
3.838 0.910 4.153 0.939 3.764 0.903
3.980 0.905 4.306 0.934 3.904 0.898
4.123 0.900 4.460 0.929 4.043 0.893
4.265 0.895 4.614 0.923 4.182 0.888
4.407 0.890 4.768 0.918 4.322 0.883
4.549 0.885 4.922 0.912 4.461 0.878
4.691 0.880 5.075 0.907 4.601 0.873
4.833 0.875 5.229 0.902 4.740 0.868
4.976 0.870 5.383 0.896 4.880 0.864
5.118 0.865 5.537 0.891 5.019 0.859
5.260 0.860 5.691 0.885 5.158 0.854
\end{filecontents}
\begin{document}
\begin{figure}[htbp]
\centering
\begin{tikzpicture}[scale=0.9]%,spy using outlines={rectangle, magnification=1.5}]
\begin{groupplot}[group style={
group name=rzrxcomp,
group size=1 by 2,
xlabels at=edge bottom,
ylabels at=edge left,
vertical sep=4em
},
xmin = 0, xmax = 2,
ymin = 0.8, ymax = 1.1,
xtick distance = 0.2,
ytick distance = 0.2,
xlabel={$time;[s]$},
ylabel={$mass$},
grid = both,
grid style = {dotted},
minor tick num = 1,
major grid style = {lightgray!75},
minor grid style = {lightgray!75},
width = 0.85\textwidth,
height = 0.50\textwidth,
legend style={at={(0.5,-0.3)},
anchor=north,legend columns=-1},
legend cell align = {left},
]
\nextgroupplot
\addplot[smooth, black, very thick] table [x = {t1}, y = {a1}] {data1.dat};
\addplot[smooth, Lavender, very thick] table [x = {t2}, y = {a2}] {data1.dat};
\addplot[smooth, Violet, very thick] table [x = {t3}, y = {a3}] {data1.dat};
\nextgroupplot[xmin = 3, xmax = 6,
ymin = 0.7, ymax = 1,
ytick distance = 0.03, legend entries={n1,n2,n3,n4}]
\addlegendimage{black, very thick, no markers}
\addlegendimage{Lavender, very thick, no markers}
\addlegendimage{Violet, very thick, no markers}
\addlegendimage{BurntOrange, dotted, very thick, no markers}
\addplot[smooth, black, very thick] table [x = {t1}, y = {a1}] {data2.dat};
\addplot[smooth, BurntOrange, dotted, very thick] table [x = {t4}, y = {a4}] {data2.dat};
\addplot[smooth, Violet, very thick] table [x = {t3}, y = {a3}] {data2.dat};
%\coordinate (spypoint) at (axis cs:xx,yy);
%\coordinate (spyviewer) at (axis cs:xx,yy);
%\spy[width=3cm,height=2cm] on (spypoint) in node [fill=white] at (spyviewer);
\end{groupplot}
\end{tikzpicture}
\end{figure}
\end{document}
I don't know if with spy it's possible to control the ytick of the spyviewer, that's why I have thought about nested groupplots. Anyway, If it could help, inside the MWE you can find commented % the spy related parts.
\draw (3.5,0.9) rectangle (4.5,1);for example, where the coordinates correspond to the axis limits of the inset axis. – Torbjørn T. Jun 26 '21 at 19:00