Chapter 12 Principal Components

We did a PCA on the dataset involving Total Votes , Total Views , Total Comments , Medal and whether it is a Competition Notebook or not.

The 1st , 2nd Principal Components explain more than 50% of the information

kvcs_versions_info = kvcs_versions_info %>%
  mutate(CompNoteBook = ifelse(is.na(SourceCompetitionId),0,1))

kvcs_reduced = kvcs_versions_info %>%
  select("TotalViews","TotalComments","TotalVotes","CompNoteBook","Medal", "MaxVersionNumber","PerformanceTier")


kvcs_reduced[is.na(kvcs_reduced)] <- 0 

kvcsPCA <- prcomp(kvcs_reduced, center = TRUE,scale. = TRUE)

std_dev <- kvcsPCA$sdev

pr_var <- std_dev^2

prop_varex <- pr_var/sum(pr_var)

summary(kvcsPCA)

## Importance of components:
##                           PC1    PC2    PC3    PC4     PC5     PC6     PC7
## Standard deviation     1.5617 1.1303 1.0202 0.9095 0.80964 0.74325 0.45574
## Proportion of Variance 0.3484 0.1825 0.1487 0.1182 0.09365 0.07892 0.02967
## Cumulative Proportion  0.3484 0.5309 0.6796 0.7978 0.89141 0.97033 1.00000

plot(cumsum(prop_varex), xlab = "Principal Component",
     ylab = "Cumulative Proportion of Variance Explained",
     type = "b")

For the First Principal Component , Total Votes , Total Comments , Total Views and Medal contributes the most . The first Principal Component explains 34% of the information
For the Second Principal Component , Performance Tier, Total Views and Whether the Notebook is a Competition Notebook or not contributes the most

12.1 Principal Component 1

showPC <- function(PCNumber) {
  kvcsPCA %>%
    tidy(matrix = "rotation") %>%
    filter(PC == PCNumber) %>%
    arrange(desc(abs(value))) %>%
    mutate(column = reorder(column,abs(value))) %>%
    ggplot(aes(x = column,y = abs(value), fill = factor(column))) +
    geom_bar(stat='identity',colour="white") +
    labs(x = 'Column', 
         y = 'Value', 
         title = 'Column and Value') +
    coord_flip() + 
    theme_fivethirtyeight() +
  theme(legend.position = "none") 
                                  
}

showPC(1)