**DRAFT:** `gnuplot`

: Cosine oscillating on arbitrary function

To let a cosine oscillate on an "arbitrary" function,
when the function goes up the *x* coordinate might go backwards,
so we can't express this as a single-valued function from *x* to *y*.
But we can use parametric curves, instead; they go from a separate parameter,
*t*, to points (*x*(*t*), *y*(*t*)). (In `gnuplot`

, this is `set parametric`

.)

As starter, here is what the final result will look like
for cosine oscillating on cosine:

(gnuplot source code of cosine on cosine)

This is what motivated myself to write up a blog post about the topic.