rbase.pdist2 {RiemBase}

Pairwise Geodesic Distances Between Two Sets of Data

Description

Unlike rbase.pdist, rbase.pdist2 takes two sets of data X=\{ x_i \}_{i=1}^m and Y=\{ y_j \}_{j=1}^m and compute mn number of pairwise distances for all i and j.

Usage

rbase.pdist2(input1, input2, parallel = FALSE)

Arguments

input1

a S3 object of riemdata class, whose $data element is of length m.

input2

a S3 object of riemdata class, whose $data element is of length n.

parallel

a flag for enabling parallel computation.

Value

an (m\times n) matrix of pairwise distances.

Examples

### Generate 10 2-frames in R^4 : as grassmann points
ndata = 10
data = array(0,c(4,2,ndata))
for (i in 1:ndata){
  tgt = matrix(rnorm(4*4),nrow=4)
  data[,,i] = qr.Q(qr(tgt))[,1:2]
}

gdata = riemfactory(data, name="grassmann")

## Compute Pairwise Distances using pdist and pdist2
A = rbase.pdist(gdata)
B = rbase.pdist2(gdata,gdata)

## Visual Comparison in Two Cases
opar = par(no.readonly=TRUE)
par(mfrow=c(1,2), pty="s")
image(A, col=gray((0:100)/100), main="pdist")
image(B, col=gray((0:100)/100), main="pdist2")
par(opar)