TP: Stereonet representation of trend and plunge

In abarbour/stress: Tools for Working with Stresses and Focal-mechanism Inversions

Description

Uses the equal-area (lower) hemispherical, or Schmidt, projection. From [1]: The main advantage of this projection method is that it does not suffer from the areal distortion of the equal angle projection. This means, for example, that an area such as that enclosed by a circle of constant radius on the projection, represents the same amount of area on the reference sphere regardless of its position. The circle will not however represent a geometrically similar circle on the sphere unless it is positioned at the centre of the projection. In other words, areal relationships are preserved in this method while geometrical relationships are distorted; the opposite is true of the equal angle projection.

Usage

TP(ang.trend, ang.plunge, r = NULL, add = FALSE, pt.pch = 16,
  pt.col = "black", pt.cex = 0.8, relpos = c(0, 0),
  dressing = TRUE, markers = TRUE, ...)

Arguments

ang.trend	numeric; trend or azimuth
ang.plunge	numeric; plunch or dip
r	numeric; the radius of the stereonet
add	logical; should the points be added to the current device?
pt.pch, pt.col, pt.cex	numeric; the symbol type(s) of the points, the color(s) of the points, and the cex(s) of the points
relpos	numeric; a vector giving the relative shift to apply to the TP projection
dressing	logical; include projection markings?
markers	logical; should markings for the projection be included? (irrelevant if !dressing)
...	additional arguments to points

Details

Uses complex, which recycles input vectors as needed

References

[1] Diederichs, Mark S (1990), Dips: An Interactive and Graphical Approach to the Analysis of Orientation Based Data, https://www.rocscience.com/documents/pdfs/uploads/7672.pdf

Examples

par(mar=rep(0,4), oma=rep(0.2,4))
TP(runif(20, min = 0, max = 90),c(45,55), xlim=c(-2,2), ylim=c(-2,2))
TP(runif(20, min = 180, max = 270),c(45,55), pt.pch=1, add=TRUE)
TP(runif(20, min = 180, max = 270),c(45,55), pt.col='red', add=TRUE, relpos=c(2,0.5), markers=FALSE)

abarbour/stress documentation built on Oct. 5, 2019, 11:20 a.m.