Filtering on a date using dplyr without changing the variable format

Question

I want use a list of years to filter a database by date

years<-c("2014")
yearsdata <- data.frame(animal=c("cow","pig"),
                        mydate=c(as.Date("2015-01-01"),
                        as.Date("2014-01-01")))
yearsdata %>% 
          mutate(mydate =format(mydate, "%Y") %>% 
          as.character()) %>%     
          filter(is.null(years) | mydate %in% years)

The above code works and lets me filter my dataset but it also formats the date column. Is there a way to get my filter results without having the format of the date column change in the finished subset dataframe?

If you don't want to format the date, then don't overwrite `mydate` with `format(mydate)`. Just make a new column `year = format(mydata, "%Y")` and you can drop it at the end `select(-year)`. (Or use lubridate like below.) — Gregor Thomas, May 12 '15 at 19:15
Are your parentheses misplaced? You have a `%>%` inside your `mutate()`! — Frank, May 12 '15 at 19:28

score 7 · Accepted Answer · answered May 12 '15 at 19:11

7

If you're up for using the lubridate package you could do:

library("lubridate")

yearsdata %>%
  filter(is.null(years) | year(mydate) %in% years)

Which gives:

#   animal     mydate
# 1    pig 2014-01-01

answered May 12 '15 at 19:11

Kara Woo

3,595
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31

score 5 · Answer 2 · answered May 12 '15 at 19:10

5

All these pipes gives me headache, I would just do

library(data.table)
setDT(yearsdata)[is.null(years) | year(mydate) %in% years]
#    animal     mydate
# 1:    pig 2014-01-01

answered May 12 '15 at 19:10

David Arenburg

91,361
17
137
196

Filtering on a date using dplyr without changing the variable format

2 Answers2