R 中有没有办法创建一个新列，以其他列为条件分配值？

Question

I have a data frame with multiples dates and associated data/variables. I'm looking to create a new column in the data frame that assigns a Yes or No variable to the new column depending on the date of the other column. For example, all dates before, say, Date1 need a 'Yes' in the new column, and all dates after Date1 need a 'No' in the new column. How do I do this?

Answer 1

The simplest way to add a new column based on a binary test is with the base R ifelse function. Here's an example using mtcars and testing for mpg >= 25 with the new columns test and test2 added to the dataframe. test2 illustrates creating a new binary column as type logical:

cars <- mtcars
cars$test <- ifelse(cars$mpg >= 25, "Yes", "No")
cars$test2 <- ifelse(cars$mpg >= 25, TRUE, FALSE)
head(cars, 5)
                   mpg cyl disp  hp drat    wt  qsec vs am gear carb test test2
Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4   No FALSE
Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4   No FALSE
Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1   No FALSE
Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1   No FALSE
Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2   No FALSE

You can use the logical comparison operators on Date values.