Skip to contents

Get instantaneous velocity for subjects

Source: R/analytical_functions.R
get_velocity.Rd

Velocity (both overall and per-axis) is computed for each row in the data (see Details)

Usage

get_velocity(
  obj_name,
  time_col = "time_sec",
  length_col = "position_length",
  width_col = "position_width",
  height_col = "position_height",
  add_to_viewr = TRUE,
  velocity_min = NA,
  velocity_max = NA,
  ...
)

Arguments

obj_name

The input viewr object; a tibble or data.frame with attribute pathviewr_steps that includes "viewr"

time_col

Name of the column containing time

length_col

Name of the column containing length dimension

width_col

Name of the column containing width dimension

height_col

Name of the column containing height dimension

add_to_viewr

Default TRUE; should velocity data be added as new columns or should this function create a new simpler object?

velocity_min

Should data below a certain velocity be filtered out of the object? If so, enter a numeric. If not, keep NA.

velocity_max

Should data above a certain velocity be filtered out of the object? If so, enter a numeric. If not, keep NA.

...

Additional arguments passed to or from other pathviewr functions.

Value

If add_to_viewr is TRUE, additional columns are appended to the input viewr object. If FALSE, a standalone tibble is created. Either way, an "instantaneous" velocity is computed as the difference in position divided by the difference in time as each successive row is encountered. Additionally, velocities along each of the three position axes are computed and provided as additional columns.

Details

Instantaneous velocity is not truly "instantaneous" but rather is approximated as the change in distance divided by change in time from one observation (row) to the previous observation (row). Each component of velocity is computed (i.e. per axis) along with the overall velocity of the subject.

See also

Other mathematical functions: calc_min_dist_v(), deg_2_rad(), find_curve_elbow(), get_2d_angle(), get_3d_angle(), get_3d_cross_prod(), get_dist_point_line(), get_traj_velocities(), rad_2_deg()

Author

Vikram B. Baliga and Melissa S. Armstrong

Examples

## Import the example Motive data included in the package
motive_data <-
  read_motive_csv(system.file("extdata", "pathviewr_motive_example_data.csv",
                             package = 'pathviewr'))

## Clean the file. It is generally recommended to clean up to the
## "standarization" step before running get_velocity().
 motive_cleaned <-
   motive_data %>%
   relabel_viewr_axes() %>%
   gather_tunnel_data() %>%
   trim_tunnel_outliers() %>%
   rotate_tunnel()

## Now compute velocity and add as columns
 motive_velocity_added <-
   motive_cleaned %>%
   get_velocity(add_to_viewr = TRUE)

## Or set add_to_viewr to FALSE for a standalone object
 motive_velocity_standalone <-
   motive_cleaned %>%
   get_velocity(add_to_viewr = TRUE)