If you let $y$ stand for $\Delta y$ and $x$ stand for $\Delta x$.
I wanted to plot this because I thought it would be interesting among other things to see the behavior of the function around $x=0$.
I'm also assuming that this function would show you the graph of all the possible derivatives of functions of 1 variable.
Sorry if this is too low-level or completely obvious. It seems kind of obvious even to me, but I've often been wrong with math when things seemed completely obvious in the past...
Yes. Look up "slope field".
For example, here:
https://en.wikipedia.org/wiki/Slope_field