Wold, H. (1966) Estimation of principal
components and related models by iterative least squares. In
P. Krishnaiah, editors.Multivariate
Analysis, Academic Press, 391–420.
Wold, S., Esbensen, K. and Geladi, P. (1987) Principal component
analysis Chemometrics and Intelligent Laboratory Systems,
2, 37–52.
See Also
dudi.pca
Examples
data(doubs)
## nipals is equivalent to dudi.pca when there are no NA
acp1 <- dudi.pca(doubs$env, scannf = FALSE, nf = 2)
nip1 <- nipals(doubs$env)
if(adegraphicsLoaded()) {
if(requireNamespace("lattice", quiet = TRUE)) {
g1 <- s1d.barchart(acp1$eig, psub.text = "dudi.pca", p1d.hori = F, plot = F)
g2 <- s1d.barchart(nip1$eig, psub.text = "nipals", p1d.hori = F, plot = F)
g3 <- xyplot(nip1$c1[, 1] ~ acp1$c1[, 1], main = "col scores", xlab = "dudi.pca",
ylab = "nipals")
g4 <- xyplot(nip1$li[, 1] ~ acp1$li[, 1], main = "row scores", xlab = "dudi.pca",
ylab = "nipals")
G <- ADEgS(list(g1, g2, g3, g4), layout = c(2, 2))
}
} else {
par(mfrow = c(2, 2))
barplot(acp1$eig, main = "dudi.pca")
barplot(nip1$eig, main = "nipals")
plot(acp1$c1[, 1], nip1$c1[, 1], main = "col scores", xlab = "dudi.pca", ylab = "nipals")
plot(acp1$li[, 1], nip1$li[, 1], main = "row scores", xlab = "dudi.pca", ylab = "nipals")
}
## Not run:
## with NAs:
doubs$env[1, 1] <- NA
nip2 <- nipals(doubs$env)
cor(nip1$li, nip2$li)
nip1$eig
nip2$eig
## End(Not run)