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I have a large dataframe in R with close to one million rows and 91 columns. For one particular column, I need to replace all negative values with "the value + 360".

All 0 or positive values should remain unchanged.

There are many solutions for setting negative values to 0, or to NA, but I can't quite get this working.

Below are examples of my attempts, with dataframe called df and feature called Bearing.

df$Bearing = apply(df$Bearing, 2, function(x){x[x<0] = x[x+360]})

df$Bearing[df$Bearing <0] <- df%Bearing +360

What is the best way to achieve my aim?

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    You can try ifelse Commented Jun 1, 2018 at 23:16

3 Answers 3

Reset to default
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Try: 

df$Bearing[df$Bearing <0] <- df$Bearing[df$Bearing <0] +360
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2 Comments

Thanks, Luke. I think there's a slight typo in your solution (% instead of $) but that's an elegant and simple solution that worked well for me, much appreciated.
Well spotted! Fixed above
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I would use

df <- within(df, Bearing <- Bearing + ifelse(Bearing < 0, 360, 0))
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If speed is an issue because of the size of your data.frame, consider using data.table. 

library(data.table)
setDT(df)
df[, bearing := ifelse(bearing < 0, bearing + 360, bearing)]
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