Skip to contents

Calculates densities for fabric and strain data

Source: R/strain_analysis.R
hypercontour.Rd

Densities in hyperbaloidal projections of geological fabric and finite strain data density calculations done on the unit hyperbaloid (Vollmer, 2018). Options are given for equidistant (Elliott), equal-area, stereographic, orthographic, exponential, and radial projections, as polar azimuthal or cylindrical (cartesian, RfPhi-type) plots.

Usage

hypercontour(
  rphi,
  angfmt = c("deg", "rad", "grd"),
  proj = c("eqd", "eqa", "stg", "ort", "gno", "lin", "rdl", "rfp"),
  normalize = TRUE,
  rmax = NULL,
  kappa = 40,
  nnodes = 50L
)

Arguments

rphi

matrix with two named columns representing the R and phi values

angfmt

character. Angle format, 'deg' for degree, 'rad' for radians, and 'grd' for gradians.

proj

character. Projection, 'eqd' for equidistant (Elliot plot), 'eqa' for equal-area, 'stg' for stereographic, 'ort' for orthographic, 'gno' for gnomonic, 'lin' for exponential (linear R), 'rdl' for radial, 'rfp' for Rf/phi (cylindrical instead of polar).

normalize

logical.

rmax

maximum R value (if NULL, computed automatically)

kappa

smoothing parameter

nnodes

grid resolution. higher is more accurate but slower, 30 is good, but 50 is recommended for final plots, default = 50.

Value

list with:

  • x, y: vectors of the projection coordinates for the density grid

  • z: density matrix

  • points: projected data points

  • frame: plot frame (circle or square)

Details

The data must be in a comma delimited csv text file with one (R, phi) pair per line, where R = strain ratio (max/min), phi = orientation of long (max) axis from x. Contours are equally spaced over the probability density distribution.

References

Vollmer, F.W., 2018. Automatic contouring of geological fabric and finite strain data on the unit hyperboloid. Computers & Geosciences, https://doi.org/10.1016/j.cageo.2018.03.006

Examples

data(ramsay)
out <- hypercontour(ramsay, angfmt = "deg", proj = 'rfp')

image(out$x, out$y, out$z, asp = ifelse(out$proj != 'rfp', 1, NA),
 ylim = c(1, out$rmax),
 xlab = bquote(varphi~'('*degree*')'), ylab = 'R',
 main = out$proj, 
col = viridis::viridis(100)
)
contour(out$x, out$y, out$z, add = TRUE, lwd = .5)
points(out$points)



out <- hypercontour(ramsay, angfmt = "deg", proj = 'eqa')
levels <- pretty(range(out$z, na.rm = TRUE), 100)
cols <- viridis::viridis(n = length(levels) - 1)
plot(out$x, y = out$y, 'n', xlab = NULL, ylab = NULL, asp = 1, axes = FALSE, ann = FALSE)
graphics::.filled.contour(out$x, out$y, out$z, levels = levels, col = cols)
points(out$points)
lines( out$frame, lwd = 2)
title(main = out$proj)