[R] Replacing null values

[Niklaus Kuehnis]

On 30.07.2011 21:58, Jeffrey Joh wrote:

> Sorry about the last message. I forgot to turn the HTML off.
> I would like to reorder a table by column A,

df2 <- df[order(df$A),]

> then fill column B with the values above it.

for (i in 1:nrow(df2)) {
     if (is.na(df2$B[i]) | df2$B[i] == "NULL") df2$B[i] <- df2$B[i-1]
}

Assumption: <NA> denotes missing value, not a character string "NA".

HTH,
Nik

> For example:
> A   B
> 2   54
> 5   NA
> 8   78
> 4   NULL
> 3   26
> 9   NULL
>
> First sort by column A:
> A   B
> 2   54
> 3   26
> 4   NULL
> 5   NA
> 8   78
> 9   NULL
>
> Then replace null/na values in column B with the value above it:
> A   B
> 2      54
> 3   26
> 4   26
> 5   26
> 8   78
> 9   78
>
> Jeff