I'm receiving an error when I'm trying to draw a group plot. What am I doing wrong?
\begin{figure}[H]
\centering
\begin{tikzpicture}
\begin{groupplot}[group style={group size=2 by 2},width=\textwidth]
\nextgroupplot[xmin = -1, xmax = 1, ymin = -1, ymax = 1,
axis lines=middle,
]
\addplot[black] (1.2,0) node[above left] {$t$};
\addplot[black] (0,.7) node[below right] {$x$};
\addplot[blue,samples=1000,domain=0:15] {x*(1-x)};
\nextgroupplot[xmin = -2, xmax = 2, ymin = -1, ymax = 1,
axis lines=middle]
\addplot[black] (1.2,0) node[above left] {$t$};
\addplot[black] (0,.7) node[below right] {$x$};
\addplot[blue,samples=1000,domain=-10:15] {x*(1-x)-((3)*rad(atan(x)))/(pi)};
\end{groupplot}
\end{tikzpicture}
\caption{Varying values for $a$ in $\dfrac{\mathrm{d}x}{\mathrm{d}t} = rx(1-x) - \frac{a}{\pi}\arctan{x}$ where $a = 0, 3, -1, 4$ (Order of graphs: left to right, up to down)}
\end{figure}
restrict x to domain
orrestrict y to domain
to adjust the range