How to conditionally replace values in r data frame using if/then statement

问题

I'd like to learn how to conditionally replace values in R data frame using if/then statements. Suppose I have a data frame like this one:

df <- data.frame(
customer_id = c(568468,568468,568468,485342,847295,847295),
customer = c('paramount','paramount','paramount','miramax','pixar','pixar'));

I'd like to do something along the lines of, "if customer in ('paramount','pixar') make customer_id 99. Else do nothing". I'm using this code, but it's not working:

if(df$customer %in% c('paramount','pixar')){
df$customer_id == 99
}else{
df$customer_id == df$customer_id
}

I get a warning message such as the condition has length > 1 and only the first element will be used. And the values aren't replaced.

I'd also like to know how to do this using logical operators to perform something like, "if customer_id >= 500000, replace customer with 'fox'. Else, do nothing.

Very easy to do in SQL, but can't seem to figure it out in R.

My sense is that I'm missing a bracket somewhere?

How do I conditionally replace values in R data frame using if/then statements?

回答1:

You can use ifelse, like this:

df$customer_id <- ifelse(df$customer %in% c('paramount', 'pixar'), 99, df$customer_id)

The syntax is simple:

ifelse(condition, result if TRUE, result if FALSE)

This is vectorized, so you can use it on a dataframe column.

回答2:

You are using == instead of =(Assignment Operator) in if block. And I dont think there's need of else block in your example as you are not going to change values

 if(df$customer %in% c('paramount','pixar')){
  df$customer_id = 99
 }

Above code will do the job for you

来源：https://stackoverflow.com/questions/48261387/how-to-conditionally-replace-values-in-r-data-frame-using-if-then-statement

标签

if-statement