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I have been using R for the past couple days and I have question that I am a little stumped on. I have a dataframe with bidder names and bids where some of the bids are empty. I am having trouble implementing a dynamic way to take the average bid for each unique bidder and apply that to the empty cells. This line of code below will take the mean bid for all of the unique bidders. All I need to do is place the mean value of unique_bid in the empty cells that shares the same bidder.

unique_bid <- aggregate(bid ~ bidder, auction[complete.cases(auction),], mean)

Here is a picture of what the dataframe looks like.

Wenfang Du
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NacDan
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1 Answers1

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You could use ave.

Example:

df = data.frame(a = c(1,1,1,2,2,2), b=c(1,2,NA,4,5,NA),c= c(1,2,3,4,5,6))

> df
  a  b c
1 1  1 1
2 1  2 2
3 1 NA 3
4 2  4 4
5 2  5 5
6 2 NA 6

Do:

sel = is.na(df$b)
df$b[sel] = ave(df$b, df$a, FUN = function(x){mean(x, na.rm = T)})[sel]

ave will use apply the function FUN to df$b while grouping by df$a. The sel will select NA elements of df$b and replace them by the correponding function's result.

Result:

> df
  a   b c
1 1 1.0 1
2 1 2.0 2
3 1 1.5 3
4 2 4.0 4
5 2 5.0 5
6 2 4.5 6
R. Schifini
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