An internal function that calculates step lengths, turning angles, and time steps for a given animal ID.

prep_data_internal(dat, coord.names)

## Arguments

dat A data frame that contains the columns associated with the x and y coordinates as well as the date-time. For easier interpretation of the model results, it is recommended that coordinates be stored after UTM projection (meters) as opposed to unprojected in decimal degrees (map units). Date-time should be of class POSIXct and be labeled date within the data frame. character. A vector of the column names under which the coordinates are stored. The name for the x coordinate should be listed first and the name for the y coordinate second.

## Value

A data frame where all original data are returned and new columns are added for step length (step), turning angle (angle), net-squared displacement (NSD), and time step (dt).