Hello,
I've done the following so far:
'> install.packages("car")
library(car)
X <- Pottery[,-1]
S = cov(X)
round(S, 2)
Al Fe Mg Ca Na
Al 8.96 -5.69 -5.21 -0.23 -0.19
Fe -5.69 5.81 4.73 0.19 0.22
Mg -5.21 4.73 4.75 0.19 0.19
Ca -0.23 0.19 0.19 0.01 0.01
Na -0.19 0.22 0.19 0.01 0.02
E = eigen(S)$vector
rownames(E) = colnames(X)
colnames(E) <- paste("PC", 1:ncol(X))
round(E, 2)
PC 1 PC 2 PC 3 PC 4 PC 5
Al 0.68 0.73 -0.04 -0.01 -0.01
Fe -0.54 0.54 0.64 -0.03 0.00
Mg -0.49 0.42 -0.77 -0.02 0.03
Ca -0.02 0.01 -0.03 -0.08 -1.00
Na -0.02 0.03 0.00 1.00 -0.08
eigen(S)$value -> L
round(L, 2)
[1] 17.24 1.77 0.52 0.01 0.00
scores = as.matrix(X) %*% E
scores.data <- data.frame(round(scores[,1:2], 2))
scores.data[,3] <- as.numeric(Pottery[,1]) # the site information
colnames(scores.data) <- c("PC scores 1", "PC scores 2", "Site")
scores.data
PC scores 1 PC scores 2 Site
1 3.90 16.11 4
2 3.88 15.34 4
3 4.20 16.12 4
4 1.61 14.20 4
5 2.95 16.13 4
6 2.32 12.80 4
7 2.48 11.46 4
8 1.87 14.06 4
9 2.36 12.97 4
10 1.82 16.54 4
11 2.32 14.76 4
12 2.61 15.46 4
13 2.84 14.75 4
14 3.08 14.26 4
15 3.15 13.20 2
16 3.13 12.96 2
17 11.45 14.34 3
18 9.16 13.10 3
19 11.12 14.24 3
20 10.91 14.45 3
21 13.00 16.31 3
22 11.18 13.77 1
23 11.52 14.27 1
24 10.62 12.92 1
25 8.27 12.57 1
26 11.83 15.09 1'
And i'm struggling to interpret the PC loadings above, I was wondering if you could help me in interpret the PC loadings I have?
Kind regards
Jennifer