tpsgrid {shapes} | R Documentation |
Thin-plate spline transformation grids from one set of landmarks to another.
tpsgrid(TT, YY, xbegin=-999, ybegin=-999, xwidth=-999, opt=1, ext=0.1, ngrid=22, cex=1, pch=20, col=2,zslice=0, mag=1, axes3=FALSE)
TT |
First object (source): (k x m matrix) |
YY |
Second object (target): (k x m matrix) |
xbegin |
lowest x value for plot: if -999 then a value is determined |
ybegin |
lowest y value for plot: if -999 then a value is determined |
xwidth |
width of plot: if -999 then a value is determined |
opt |
Option 1: (just deformed grid on YY is displayed), option 2: both grids are displayed |
ext |
Amount of border on plot in 2D case. |
ngrid |
Number of grid points: size is ngrid * (ngrid -1) |
cex |
Point size |
pch |
Point symbol |
col |
Point colour |
zslice |
For 3D case the scaled z co-ordinate(s) for the grid slice(s). The values are on a standardized scale as a proportion of height from the middle of the z-axis to the top and bottom. Values in the range -1 to 1 would be sensible. |
mag |
Exaggerate effect (mag > 1). Standard effect has mag=1. |
axes3 |
Logical. If TRUE then the axes are plotted in a 3D plot. |
A square grid on the first configuration is deformed smoothly using a pair of thin-plate splines in 2D, or a triple of splines in 3D, to a curved grid on the second object. For 3D data the grid is placed at a constant z-value on the first figuure, indicated by the value of zslice.
For 2D data the covariance function in the thin-plate spline is $sigma(h) = |h|^2 log |h|^2$ and in 3D it is given by $sigma(h) = -| h |$.
No returned value
Ian Dryden
Bookstein, F.L. (1989). Principal warps: thin-plate splines and the decomposition of deformations, IEEE Transactions on Pattern Analysis and Machine Intelligence, 11, 567–585.
Dryden, I.L. and Mardia, K.V. (1998) Statistical Shape Analysis. Wiley, Chichester. Chapter 10.
procGPA
data(gorf.dat) data(gorm.dat) #TPS grid with shape change exaggerated (2x) gorf<-procGPA(gorf.dat) gorm<-procGPA(gorm.dat) TT<-gorf$mshape YY<-gorm$mshape tpsgrid(TT,YY,mag=2) title("TPS grid: Female mean (left) to Male mean (right)")