Mapping substr of dataframe to new column [duplicate]-CodePudding

I would like to map the first/second characters of the column ï..Order.Date to a new column called Order.Month.

ï..Order.Date is a column in the data frame with string dates in M/D/YY or MM/DD/YY format:

"12/1/17" "9/1/17" "9/19/17" "9/1/17" "9/29/17"

I need to create a new column which uses the substring containing the first 1 or 2 characters, and map it to the month:

months = c('January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December')

Still new to r and not sure the best way to approach this.

CodePudding user response：

We can convert the column to Date class, get the month extracted, convert to numeric and use as index to get the value that corresponds to from the built-in vector month.name

df1$Order.Month <- month.name[as.integer(format(as.Date(df1[["ï..Order.Date"]], 
        format =  "%m/%d/%y"), "%m"))]

Or use lubridate - convert to Date class with mdy, extract the month, use as index in month.name

library(lubridate)
month.name[month(mdy(df1[["ï..Order.Date"]]))]

CodePudding user response：

Once you create a date object you can use format(..., '%B') to get the month name.

x <- c("12/1/17", "9/1/17", "9/19/17", "9/1/17", "9/29/17")
format(lubridate::mdy(x), '%B')

#[1] "December"  "September" "September" "September" "September"