Basically I'm tasked with making a simple phonebook in R.
I've made a large array which each entry following this pattern (FirstName LastName PhoneNumber, FirstName LastName PhoneNumber, etc.)
I need to do a simple print of someones info, like say first name was John it would return me all indexes starting with john.
I know I need an if statement but I do not know the proper syntax that I could just identify the beginning of the string. Can anyone help me?
x <- c('Mary Higgins', 'John Williams', 'Zhu Wang', 'Peter Johnson')
# all elements containing John
grep('John', x)
#[1] 2 4
# starting with John
grep('^John', x)
#[1] 2
From this question: Test if characters in string in R
chars <- "test"
value <- "es"
grepl(value, chars)
You don't need an if statement, and I would try to avoid those in general (they're slow and sometimes convoluted to work with). You could try:
data <- data.frame(FirstName = c('Mary', 'John', 'Zhu', 'Peter'),
LastName = c('Higgins', 'Williams', 'Wang', 'Johnson'),
PhoneNumber = c("234-234-2342", "456-456-4564", "678-678-6788", "345-345-3455"))
data %>%
filter(FirstName == "John")
You can use a regular expression with ^ to specify that John is at the very beginning of the string. E.g.,
names <- c("John Hogg", "Hogg John")
grep("^John", names)
[1] 1
Alternatively, you could use startswith:
startsWith(names, "John")
[1] TRUE FALSE
