optim_roughness: Compute the optimal smoothing parameter of slope_FUN
In jaromilfrossard/permucoSlope: Extension of the permuco package

Find smoothing paramters that matches rougness of original signal and of their slope

optim_roughness(
  y,
  slope_FUN,
  par = 0.5,
  avg_FUN = mean,
  roughness_FUN = roughness,
  method = c("Brent"),
  lower = 0,
  upper = 1
)

`y`	matrix of the signals.
`slope_FUN`	function that compute the slope
`par`	initial value of the smoothing paramter. Default is 0.5.
`avg_FUN`	function to aggregate the rougness of each signal. Defaults is the method.
`roughness_FUN`	function of roughness to optimize
`method`	optimizer from `optim`. Defaults is "Brent".
`lower`	a scalar indicating the lower bound of `par`.
`upper`	a scalar indicating the upper bound of `par`.