CS计算机代考程序代写 # BS1033 Lecture 8 Analysis
# BS1033 Lecture 8 Analysis
# Author: Chris Hansman
# Email: chansman@imperial.ac.uk
# Date : 25/02/20
#Loading Libraries
library(tidyverse)
#Function to Plot Images
plt_img <- function(x){
image(matrix(as.numeric(x), nrow = 64, byrow = T),
col = grey(seq(0, 1, length = 256)))
}
#Loading Face Data (Faces are Rows)
faces <- read_csv("olivetti.csv") %>%
as.matrix()
#Plotting One ca
plt_img(faces[105,1:4096])
#Loading Labels
y_df<- sort(rep(1:40, times = 10))
# Look for the average face for each person.
#Group by label then take average of every variable (pixel)
AverageFace <- data.frame(faces) %>%
mutate(label=y_df) %>%
group_by(label) %>%
summarise_all(mean)
#Plot
plt_img(AverageFace[1, 2:4097]) # For 1st subject
#PCA
pc <- prcomp(faces, center = T, scale=F)
eigenvalues <- as.matrix((pc$sdev^2))
eigenvectors <- as.matrix(pc$rotation)
princomp <- pc$x
#Recovering Initial Photos
recover <- eigenvectors%*%t(pc$x)+ pc$center
plt_img(recover[,12]) # For 1st subject
plt_img(faces[12,1:4096])
#First 40 Eigenvalues Explain 85% of the variance
sum(eigenvalues[1:40])/sum(eigenvalues)
#Selecting Those:
eigen40=eigenvectors[,1:40]
princomp40 <- pc$x[,1:40]
center=pc$center
#Recreating Images with Just the first 40 Principle Components
recover <- eigen40%*%t(princomp40)+ pc$center
plt_img(recover[,30])
plt_img(faces[30,])
#Projecting a photo onto first 40 eigenvalues:
PF1 <- as.matrix((faces[88,]-center)%*%eigen40)
PFall <-princomp40 # as.matrix(faces-center)%*%eigen40
#Closest Options
test <- matrix(rep(1,400),nrow=400,byrow=T)
test_PF1 <- test %*% PF1
Diff <- PFall-(test_PF1)
a <- diag(Diff%*%t(Diff))
# Find the Most Similar Faces
y <- diag(Diff%*%t(Diff))
x=c(1:400)
newdf=data.frame(cbind(x,y))
a<-newdf[order(newdf[,2]),]
a[1:10,]
plt_img(faces[88,])
plt_img(faces[84,])
