I’m trying to compare each date (find maximum value/latest date) for each row in a data frame column with a single date.
For example:
date
1 2018-07-31
2 2018-08-01
3 2018-08-02
4 2018-08-03
When I compare to compare_date="2018-08-02", it should give an output of the latest date between each row and the compare_date. So the new data frame would look like this:
new_date
1 2018-08-02
2 2018-08-02
3 2018-08-02
4 2018-08-03
I’m trying to use sapply to this problem:
data$new_date <- sapply(data$date,function(x){max(x,compare_date)})
But I got the output not in a date format, like this:
date new_date
1 2018-07-31 17745
2 2018-08-01 17745
3 2018-08-02 17745
4 2018-08-03 17746
Please Note that I had converted the data$date and compare_date to Date format using as.Date.
Why is the output not in a date format? Am I using sapply in the wrong way?
>Solution :
There are vectorised functions available in R to do this instead of using sapply. In this case, you can use pmax –
df$date <- as.Date(df$date)
compare_date=as.Date("2018-08-02")
df$date <- pmax(df$date, compare_date)
df
# date
#1 2018-08-02
#2 2018-08-02
#3 2018-08-02
#4 2018-08-03
data
df <- structure(list(date = c("2018-07-31", "2018-08-01", "2018-08-02",
"2018-08-03")), class = "data.frame", row.names = c(NA, -4L))