Question about REM density

[laura-hainke]

Hello, how is rapid eye movement density calculated with YASA? After using rem_detect() and summary(), the parameter "Density" is shown, but what is the unit? Thank you!

[raphaelvallat]

Hi @laura-hainke,

The density parameter is the number of events per minute:

yasa/yasa/detection.py

Lines 220 to 233 in b1e866c

	# Calculate density (= number per min of each stage)
	if self._hypno is not None and grp_stage is True:
	stages = np.unique(self._events["Stage"])
	dur = {}
	for st in stages:
	# Get duration in minutes of each stage present in dataframe
	dur[st] = self._hypno[self._hypno == st].size / (60 * self._sf)
	# Insert new density column in grouped dataframe after count
	df_grp.insert(
	loc=df_grp.columns.get_loc("Count") + 1,
	column="Density",
	value=df_grp.apply(lambda rw: rw["Count"] / dur[rw["Stage"]], axis=1),
	)

Thanks,
Raphael

[laura-hainke]

Thanks for clarifying, Raphael!

[remrama]

Probably worth adding this quickly to the documentation before closing the issue. (I'll do it.)