############################################################
## R code to reproduce statistical analysis in the textbook:
## Agresti, Franklin, Klingenberg
## Statistics: The Art & Science of Learning from Data
## 5th Edition, Pearson 2021
## Web: ArtofStat.com
## Copyright: Bernhard Klingenberg
###########################################################

###################
###  Chapter 2  ###
###  Example 7  ###
###################

###############
## Histogram ##
###############

# Read in Sodium values:
sodium <- c(0, 340, 70, 140, 200, 180, 210, 150, 100, 130, 
            140, 180, 190, 160, 290, 50, 220, 180, 200, 210)

# Create Basic Histogram:
hist(sodium, col = 'tan', 
     main = 'Distribution of Sodium Values in Cereals',
     xlab = 'Sodium (mg)', ylab = 'Frequency')

# Changing the bins by providing the boundaries.
# (Note: right=FALSE puts an observation such as 120 in the interval from 120-160 and not 80-120)
hist(sodium, breaks = seq(0,360,40), right = FALSE, col = 'tan', 
     main = 'Distribution of Sodium Values in Cereals', 
     xlab = 'Sodium (mg)', ylab = 'Frequency')

# Another way to request a certain number of bins:
hist(sodium, breaks = 10,  col = 'tan', 
     main = 'Distribution of Sodium Values in Cereals',
     xlab = 'Sodium (mg)', ylab = 'Frequency')

# Too few breaks:
hist(sodium, breaks = 2, col = 'tan',
     main = 'Distribution of Sodium Values in Cereals',
     xlab = 'Sodium (mg)', ylab = 'Frequency')

# Too many breaks:
hist(sodium, breaks = 30, col = 'tan',
     main = 'Distribution of Sodium Values in Cereals',
     xlab = 'Sodium (mg)', ylab = 'Frequency')

# For more fine tuning, it is better to use the ggplot2 library.
# If you haven't installed it already, first type: install.packages(ggplot2)
library(ggplot2)

# Adjusting x-axis labels:
ggplot(data.frame(sodium), aes(x = Sodium)) + 
  geom_histogram(breaks = seq(0,360,40), color="black", fill="tan") +
  labs(x = 'Sodium (mg)', y = 'Frequency',  
       title="Distribution of Sodium Values in Cereals") +
  scale_y_continuous(limit = c(0,7), 
                     breaks = 1:7, 
                     expand = c(0,0)) +
  scale_x_continuous(breaks = seq(0,360,40)) +
  theme_bw() +
  theme(panel.grid.minor = element_blank(), 
        text=element_text(size = 14))

# Plotting percentages rather than counts on the y-axis:
ggplot(data.frame(sodium), 
       aes(x = sodium, y = 100 * (..count.. / sum(..count..)))) + 
  geom_histogram(breaks = seq(0,360,40), color = 'black', fill = 'tan') +
  labs(x = 'Sodium (mg)', y = 'Percent (%)',  
       title = 'Distribution of Sodium Values in Cereals') +
  scale_y_continuous(limit = c(0,32), 
                     breaks = seq(0,30,5), 
                     expand = c(0,0)) +
  scale_x_continuous(breaks = seq(0,360,40)) +
  theme_bw() +
  theme(panel.grid.minor=element_blank())

# R actually defines intervals open to the left and closed to the right 
# To get the histograms perfectly match the ones in the textbook, use closed="left":
ggplot(data.frame(sodium), 
       aes(x = sodium, y = 100 * (..count.. / sum(..count..)))) + 
  geom_histogram(breaks = seq(0,360,40), closed = 'left', color = 'black', fill = 'tan') +
  labs(x = 'Sodium (mg)', y = 'Percent (%)',  
       title = 'Distribution of Sodium Values in Cereals') +
  scale_y_continuous(limit = c(0,32), 
                     breaks = seq(0,30,5), 
                     expand = c(0,0)) +
  scale_x_continuous(breaks = seq(0,360,40)) +
  theme_bw() +
  theme(panel.grid.minor = element_blank())