Strings

Question 1

toupper(vector_argument)

Answer 1

• Function that makes all the letters of the entries to upper case.
• Use with strings.

Question 2

tolower(vector_argument)

Answer 2

• Function that makes all the letters of the entries to lower case.
• Use with strings.

Question 3

gsub(“thing_to_remove”, “thing_to_replace_with”, what_I_want_to_remove_it_from)

Answer 3

• A function that performs “global” substitutions.
• Will substitute every occurrence of something.
• | (vertical bar) is “or” in a gsub().
• \s is interpreted as white space.
• \s+ means one or more occurrences of white spaces.
• \s+$ does \s+ matches to the end of the lines.
• =! means “not equal to”.
• ^\s+ does \s+ for spaces before the name.
• KNOW HOW TO REPLACE A COMA AND A DOLLAR SIGN (gsub(“\$|,”,”“,money) will strip all $ and , from money).

Question 4

Regular Expression

Answer 4

• Provides a concise + flexible way to specify or recognize strings.
• Its main purpose is to search, and maybe, replace.

Question 5

na.rm = TRUE

Answer 5

• An option when using function mean() to remove all missing values so that the resulting mean is not NA.

Question 6

grep()

Answer 6

• Function used to search strings and match patterns.

Question 7

grepl()

Answer 7

• Function used to search strings and matching patterns and will indicate whether it found the pattern in the string.

Question 8

nchar()

Answer 8

• Function that counts the number of characters in a string, which includes spaces.

Question 9

paste()

Answer 9

• Function that creates longer strings from shorter ones.
• Useful for making variable names.
• Clearest application of the recycling rule.

Question 10

strsplit()

Answer 10

• Function that splits strings according to a specific “split”.
• Outputs a list.
• Need to use unlist to convert this list to a vector.

Question 11

which(object_name, %in% “word_we_want”)

Answer 11

• Function that acts a locator for something in a vector and returns the indexes of where the occurrences happen.