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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?

Julia McDonough
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    Welcome to SO, Julia McDonough! Please make this question *reproducible*. This includes sample code you've attempted (including listing non-base R packages, and any errors/warnings received), sample *unambiguous* data (e.g., `data.frame(x=...,y=...)` or the output from `dput(head(x))`), and intended output given that input. Refs: https://stackoverflow.com/q/5963269, [mcve], and https://stackoverflow.com/tags/r/info. – r2evans Oct 25 '21 at 17:43
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    But another thought: there are literally dozens of questions asked *each week* that ask almost the same title/question. Please search around SO for similar questions. It will likely be a much better solution for you: (1) you can see many already-written solutions to similar problems without waiting for us to see, attempt, and answer; and more important (2) we don't have your data and you've provided no attempted effort or code, so the chance of somebody guessing is really low. Please read the links I provided above, they can be quite helpful, helping you to get better answers, faster. Thanks! – r2evans Oct 25 '21 at 17:45
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    Does this answer your question? [Can dplyr package be used for conditional mutating?](https://stackoverflow.com/questions/24459752/can-dplyr-package-be-used-for-conditional-mutating) – Karl Oct 25 '21 at 17:49

1 Answers1

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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.

SteveM
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