Data Frames, object structure in R

DataFrameSample.R

# create a data frame
user_df <- data.frame(
    name = c("Alice", "Bob", "Charlie", "Dave"),
    age = c(25, 32, 47, 19),
    city = c("New York", "San Francisco", "Los Angeles", "Chicago"),
    stringsAsFactors = FALSE
)

# view the data frame
user_df

# access to the 3rd age (Charlie's age)
user_df$age[3] # show: 47

# show all elements of 3rd user (Charlie)
user_df[3,] # show: Charlies, 47, Los Angeles

pH per season and main European cities.R

# Note: the below pH information is made up as for this example and doesn't reflect to the reality
my.database <- data.frame(
    Cities = c("London", "Paris", "Berlin", "Amsterdam"),
    Season=c("Winter", "Summer", "Spring", "Autumn"),
    pH = c(7.4, 6.3, 3.4, 5.7)
)

my.database


# filter pH greater than 6 and show the "Cities"
# output: "London" "Paris" 
my.database[my.database$pH > 6, "Cities"]

# output: Cities Season  pH
#         London Winter 7.4
my.database[my.database$Season == "Winter",]