Derive center of pressure from a pressure movie

Computes the pressure-weighted centroid at each frame. Grid columns define the mediolateral (cop_x) direction and rows define the anteroposterior (cop_y) direction, matching calculateCOP() and swayMetrics().

Usage

copFromPressure(pm, contact_threshold = 0)

Arguments

pm

A pressure_movie.

contact_threshold

Pressure threshold in kPa. Values at or below the threshold do not contribute to force or center of pressure.

Value

A data frame with time, cop_x, cop_y, total_force, and contact_area. CoP coordinates are in mm and force is in N.

References

Pataky TC (2012). Spatial resolution in plantar pressure measurement revisited. Journal of Biomechanics, 45:2116-2124.

See also

swayMetrics(), calculateCOP()

Examples

x <- array(0, c(3, 3, 2))
x[2, 3, ] <- 100
copFromPressure(pressureMovie(x, 100, dx = 5, dy = 5))
#>   time cop_x cop_y total_force contact_area
#> 1 0.00  12.5   7.5         2.5           25
#> 2 0.01  12.5   7.5         2.5           25