Convenient wrapper to `signal::interp1()`

for linear
interpolation. Assumes that you want interpolated values of
`xy_old`

at `n_xy_new`

equidistant data points.

## Arguments

- time_old
Timestamps of the

`xy_old`

coordinates.- xy_old
To-be normalized x or y coordinates.

- n_xy_new
Number of equidistant timepoints that should be generated. Defaults to 101.

## References

Wirth, R., Foerster, A., Kunde, W., & Pfister, R. (2020). Design choices: Empirical recommendations for designing two-dimensional finger tracking experiments. Behavior Research Methods, 52, 2394 - 2416. doi:10.3758/s13428-020-01409-0

## Examples

```
plot(interp2(0:10, (0:10)^2))
```