CODEWITHSUNDEEP
r
elea
elea

Reputation: 23

Create vector of appended dates in R

I have a data frame (set1) with 3 fields - date (date), price (numeric) and event (logical). I would like to create a vector that returns the date when event is TRUE.

I have been able to do this for price: returns a vector of 346 prices

n <- c()
for(i in 1:length(set1$price)){
    if(set1$event[i] == TRUE) {
      n <- append(n,set1$price[i])
  }
}

However, when I try to do the same for date only the first date when event is TRUE is returned: 2001-10-29

n <- c()
for(i in 1:length(set1$date)){
    if(set1$event[i] == TRUE) {
      n <- append(n,set1$date[i])
  }
}

I tried to assign the empty vector as a date field but the result was still the same:

n <- c()
n <- as.Date(as.character(n), format = "%Y%m%d")

Upvotes: 2

Views: 194

Answers (1)

Rich Scriven
Rich Scriven

Reputation: 99331

You can use [ subsetting on the logical vector event. For example, here's some made-up data

date <- seq(Sys.Date()-5, Sys.Date(), 1)
event <- c(FALSE, TRUE, TRUE, FALSE, FALSE, TRUE)
(set1 <- data.frame(date, event))
#         date event
# 1 2014-11-09 FALSE
# 2 2014-11-10  TRUE
# 3 2014-11-11  TRUE
# 4 2014-11-12 FALSE
# 5 2014-11-13 FALSE
# 6 2014-11-14  TRUE

Then you can subset the date vector by the event vector and all the dates for which event is TRUE will be returned.

with(set1, date[event])
# [1] "2014-11-10" "2014-11-11" "2014-11-14"

And you could do the same for the pricing column in your data.

Upvotes: 1

Related Questions