coo_samplerr: Samples coordinates (regular radius)

Description

Samples n coordinates with a regular angle.

Usage

coo_samplerr(coo, n)

Value

a matrix of (x; y) coordinates or a Coo object.

Arguments

coo: matrix of (x; y) coordinates or any Coo object.
n: integer, the number of points to sample.

Details

By design, this function samples among existing points, so using coo_interpolate prior to it may be useful to have more homogeneous angles. See examples.

Other coo_ utilities: coo_aligncalliper(), coo_alignminradius(), coo_alignxax(), coo_align(), coo_baseline(), coo_bookstein(), coo_boundingbox(), coo_calliper(), coo_centdist(), coo_center(), coo_centpos(), coo_close(), coo_down(), coo_dxy(), coo_extract(), coo_flipx(), coo_force2close(), coo_interpolate(), coo_is_closed(), coo_jitter(), coo_left(), coo_likely_clockwise(), coo_nb(), coo_perim(), coo_range(), coo_rev(), coo_right(), coo_rotatecenter(), coo_rotate(), coo_sample_prop(), coo_sample(), coo_scale(), coo_shearx(), coo_slice(), coo_slidedirection(), coo_slidegap(), coo_slide(), coo_smoothcurve(), coo_smooth(), coo_template(), coo_trans(), coo_trimbottom(), coo_trimtop(), coo_trim(), coo_untiltx(), coo_up(), is_equallyspacedradii()

Examples

Run this code

stack(bot)
bot <- coo_center(bot)
stack(coo_samplerr(bot, 12))
coo_plot(bot[1])
coo_plot(rr <- coo_samplerr(bot[1], 12))
cpos <- coo_centpos(bot[1])
segments(cpos[1], cpos[2], rr[, 1], rr[, 2])

# Sometimes, interpolating may be useful:
shp <- hearts[1] %>% coo_center

# given a shp, draw segments from each points on it, to its centroid
draw_rads <- function(shp, ...){
 segments(shp[, 1], shp[, 2], coo_centpos(shp)[1], coo_centpos(shp)[2], ...)
}

# calculate the sd of argument difference in successive points,
# in other words a proxy for the homogeneity of angles
sd_theta_diff <- function(shp)
   shp %>% complex(real=.[, 1], imaginary=.[, 2]) %>%
   Arg %>% `[`(-1) %>% diff %>% sd

# no interpolation: all points are sampled from existing points but the
# angles are not equal
shp %>% coo_plot(points=TRUE, main="no interpolation")
shp %>% coo_samplerr(64) %T>% draw_rads(col="red") %>% sd_theta_diff
# with interpolation: much more homogeneous angles
shp %>% coo_plot(points=TRUE)
shp %>% coo_interpolate(360) %>% coo_samplerr(64) %T>% draw_rads(col="blue") %>% sd_theta_diff