Strings

Format numbers

sprintf("%02.1f%%", your_number) # (1)
# Output: "xxxx.x%"

sprintf("Pi to 3 decimal places: %.3f", pi)
# Output: "Pi to 3 decimal places: 3.142"

sprintf("Scientific notation of Pi: %e", pi) # (2)
# Output: "Scientific notation of Pi: 3.141593e+00"

sprintf("%s is %d years old", "Alice", 25) # (3)
# Output: "Alice is 25 years old"

1. • %%: Literal %
   • %f: Double precision value in fixed-point notation
2. %e, %E: Double precision value in exponential notation
3. • %d, %i: Integer value
   • %s: Character string

Regular expression

Extract anything between certain words

stringr::str_extract_all(
          string  = .x,
          pattern = "(?<=using last ).+(?= days)" # between the word 'using last ' and ' days'
        )

substitute the last dash with nothing

sub('-[^-]*$', '', sentence) # (1)

1. matching a dash followed by zero or more characters that are not a dash till the end ($) of the string and replace it with blank ('')

Replace

# Replace multiple strings at a time
rep_str = c('St'='Street','Blvd'='Boulevard','Pkwy'='Parkway')
df$address <- str_replace_all(df$address, rep_str)

String pad

Pad a string to a fixed width.

rbind(
  str_pad(string = "hadley", width = 30, side = "left",pad = "."),
  str_pad("hadley", 30, "right"),
  str_pad("hadley", 30, "both")
)

# All arguments are vectorised except side
str_pad(c("a", "abc", "abcdef"), 10)
str_pad("a", c(5, 10, 20))
str_pad("a", 10, pad = c("-", "_", " "))

data %>% pwalk(
        .,
        ~ cat(str_pad(..2, 18, side = 'right', '.'), ..3, '\n') 
        #..2 = col #2 as the string, side = put pad at right
      )