roi.analysis: Execute a ROI analysis on movement data
In dgromer/movhm: Functions for displaying movement data of groups as heatmaps.

Execute a ROI analysis on movement data

1	roi.analysis(..., x, y, roi, blocksize, margins, consider.time = FALSE)

`...`	lists of two-column data frames with x- and y-values
`x`	name of the column containing x-values in the data frames in `...` (string)
`y`	name of the column containing y-values in the data frames in `...` (string)
`roi`	a two-column data frame with x- and y-values specifying what cells should be included in the ROI.
`blocksize`	scaling factor
`margins`	numeric vector of length 4 containing the margins (xmin, ymin, xmax, ymax)
`consider.time`	logical indicating whether to count one subject multiple times in one cell