# Let’s combine them!

It is possible to combine two or more plots into one picture.

For example, we solve the following initial-value problem

$\begin{cases} \frac{dy}{dx} = (x-y)/2 \\ y(0)=1 \end{cases}\quad\quad\quad(\star)$

and plot the analytic solution in Fig. 1.

Fig. 1

We can also solve $(\star)$ numerically and plot the discrete data points:

Fig. 2

Fig. 3 is the result of combining Fig.1 and Fig. 2.

Fig.3

It validates the numerical solution obtained by ‘rk’: the two figures clearly overlapped.