CODEWITHSUNDEEP
rreplace
adam.888
adam.888

Reputation: 7846

R replacing zeros in dataframe with next non zero value

I have a dataframe with a column containing zero values:

a <- 1:10
b <- c(1, 0, 0, 0, 0, -1, -1, 0, 0, 1)
df <- data.frame(a, b)
df

How can I replace the zero values with the last non zero value ie column df$b to be:

 1,-1,-1,-1,-1,-1,-1,1,1,1

Thank you for your help.

Upvotes: 5

Views: 2440

Answers (1)

Rich Scriven
Rich Scriven

Reputation: 99331

Here's one way with na.locf from zoo. Although this method does change some values to NA in the process, the code is nice and painless.

library(zoo)
na.locf(with(df, ifelse(b == 0, NA_real_, b)), fromLast = TRUE)
# [1]  1 -1 -1 -1 -1 -1 -1  1  1  1

An alternative to this, and one that might be faster than ifelse on long vectors, is

na.locf(with(df, { is.na(b) <- b == 0; b }), fromLast = TRUE)
# [1]  1 -1 -1 -1 -1 -1 -1  1  1  1

Upvotes: 8

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