In just a few words of plain English, what does the following function do? Don’t immediately run the code! Try to provide some explanation for your answer first, then run the code to check your answer.
library(stringr)
f <- function(n) {
for (i in seq(n)) {
a = str_c(rep("*", i), collapse = '')
cat(a, '\n')
}
}In your own words, describe the difference between the
sep and collapse arguments to
str_c().
What does str_trim() do? What’s the opposite
function of str_trim()?
What does splitting a string with an empty string
("") do? For example, what would
str_split('hello world', '') return?
Here are a bunch of functions you should be able to write. Any of these may appear (directly or modified) on a quiz or exam!
reverseString(s)Write a function that returns the string s in reverse
order. So if s equals "abcde",
reverseString(s) should equal "edcba". You may
assume that s only contains upper and/or lower case
letters, but your solution must correctly return capital letters in
their appropriate order. For example,
reverseString("aWordWithCaps") should return
"spaChtiWdroWa".
isPalindrome(s)Write a function that returns TRUE if the string
s is a Palindrome and
FALSE otherwise. The string s can contains any
letter, number, or symbol, but it will be a character data type.
sortString(s)Write the function sortString(s) that takes a string
s and returns back an alphabetically sorted string. So
sortString("cba") should return "abc". You may
assume that s only contains upper and/or lower case
letters.
letterCount(s)Write the function letterCount(s) that takes a string
s and returns a named vector with the count of each letter
in s, spanning the alphabet. If a letter does not appear in
s, it should have a value of 0. You may assume
that s only contains upper and/or lower case letters. You
should ignore cases, so "a" and "A" should be
both treated as "a".
For example, letterCount("aaaaabbbc") should return:
a b c d e f g h i j k l m n o p q r s t u v w x y z
5 3 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0And letterCount("someString") should return:
a b c d e f g h i j k l m n o p q r s t u v w x y z
0 0 0 0 1 0 1 0 1 0 0 0 1 1 2 0 0 1 2 1 0 0 0 0 0 0areAnagrams(s1, s2)Background: An anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.
With that in mind, write the function
areAnagrams(s1, s2) that takes two strings, s1
and s2 (that you may assume contain only upper and/or lower
case letters), and returns TRUE if the strings are
anagrams, and FALSE otherwise. Treat "a" and
"A" as the same letters (so "Aba" and
"BAA" are anagrams). Hint: you may want to use either
letterCount(s) or sortString(s) as helper
functions - each are helpful for different approaches.
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