The ifelse() function in base R converts date objects to numeric objects by default.

To prevent this from happening, you can use one of the following methods as an alternative:

Method 1: Use as.character() in Base R

df$date <- as.Date(ifelse(df$date < '2022-01-20',
                   as.character(df$date+5),
                   as.character(df$date)))

Method 2: Use if_else() in dplyr

df$date <- if_else(df$date < '2022-01-20', df$date+5, df$date)

Method 3: Use fifelse() in data.table

df$date <- fifelse(df$date < '2022-01-20', df$date+5, df$date)

The following examples show how to use each method in practice with the following data frame in R:

#create data frame
df <- data.frame(date=as.Date(c('2022-01-05', '2022-01-17', '2022-01-22',
                        '2022-01-23', '2022-01-29', '2022-02-13')),
                 sales=c(22, 35, 24, 20, 16, 19))

#view data frame
df

        date sales
1 2022-01-05    22
2 2022-01-17    35
3 2022-01-22    24
4 2022-01-23    20
5 2022-01-29    16
6 2022-02-13    19

Example 1: Use as.character() in Base R

The following code shows how to use the as.character() function with the ifelse() function from base R to perform an if else statement on the date column in the data frame and produce a date as a result:

#if date is before 2022-01-20 then add 5 days
df$date <- as.Date(ifelse(df$date < '2022-01-20',
                   as.character(df$date+5),
                   as.character(df$date)))

#view updated data frame
df

        date sales
1 2022-01-10    22
2 2022-01-22    35
3 2022-01-22    24
4 2022-01-23    20
5 2022-01-29    16
6 2022-02-13    19

If any value in the date column was before 2022-01-20, we added five days to the date.

Notice that the date column has retained its date format instead of being converted to a numeric format.

Example 2: Use if_else() in dplyr

The following code shows how to use the if_else() function from dplyr to perform an if else statement on the date column in the data frame and produce a date as a result:

library(dplyr)

#if date is before 2022-01-20 then add 5 days
df$date <- if_else(df$date < '2022-01-20', df$date+5, df$date)

#view updated data frame
df

        date sales
1 2022-01-10    22
2 2022-01-22    35
3 2022-01-22    24
4 2022-01-23    20
5 2022-01-29    16
6 2022-02-13    19

If any value in the date column was before 2022-01-20, we added five days to the date.

Notice that the date column has retained its date format instead of being converted to a numeric format.

Example 3: Use fifelse() in data.table

The following code shows how to use the fifelse() function from data.table to perform an if else statement on the date column in the data frame and produce a date as a result:

library(data.table)

#if date is before 2022-01-20 then add 5 days
df$date <- fifelse(df$date < '2022-01-20', df$date+5, df$date)

#view updated data frame
df

        date sales
1 2022-01-10    22
2 2022-01-22    35
3 2022-01-22    24
4 2022-01-23    20
5 2022-01-29    16
6 2022-02-13    19

If any value in the date column was before 2022-01-20, we added five days to the date.

Once again, the date column has retained its date format instead of being converted to a numeric format.

Note: For extremely large data frames, the dplyr and data.table methods will be faster than the base R method.