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Created March 30, 2023 13:30
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Lecture notes and solutions to the in-class exercises of session 4 in the spring semester 2023.
Lecture notes and solutions to the in-class exercises of session 4 in the spring semester 2023.
library(tibble)
# Task 1-------------------------------
# Create a factor with the levels "still", "medium", "sparkling",
# and arbitrary instances of the three levels
# Get the relative frequencies for "medium" of this factor
# Task 2-------------------------------
# Create a data frame with two columns, one called "nb" containing the
# numbers 1 to 5 as double, the other called "char" containing the
# numbers 6 to 10 as character
# Transform this data frame into a tibble!
# Extract the second column of this tibble such that you have a vector
# Advanced object types================
library(tibble)
library(dplyr)
## Factors-----------------------------
# Define a factor:
f_1 <- factor(
x = c(rep("F", 4),
rep("D", 5),
rep("M", 3)),
levels = c("D", "F", "M")
)
f_1
levels(f_1) # Get the levels
# What happens if we do not specify levels explicitly?
f_2 <- factor(
x = c(rep("F", 4),
rep("D", 5),
rep("M", 3))
)
f_2
levels(f_2) # Get the levels
# What happens if the vector contains elements not pre-specified as levels?
f_3 <- factor(
x = c(rep("F", 4),
rep("D", 5),
rep("M", 3)),
levels = c("F", "M")
)
f_3
levels(f_3) # Get the levels
typeof(f_3)
is.factor(f_3)
## data.frames and tibbles-----------------------
l_1 <- list(
"gender" = c(rep("male", 3), rep("female", 2)),
"height" = c(189, 175, 180, 166, 150)
)
df_1 <- data.frame(
"gender" = c(rep("male", 3), rep("female", 2)),
"height" = c(189, 175, 180, 166, 150)
)
tb_1 <- tibble::as_tibble(df_1)
# What’s the difference between [ and [[?
tb_1["gender"] # Returns the column as a one-column tibble
tb_1[["gender"]] # Returns the underlying vector
c(tb_1[["gender"]], "male") # works as expected
c(tb_1["gender"], "male") # produces weird result
# How do you think you can test for the type of a column vector?
typeof(tb_1[["gender"]]) # NOT typeof(tb_1["gender"])
dplyr::glimpse(tb_1)
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