[R] HELP ME: Fill NA Values from the previous Non-NA Values

[William Dunlap]

You could use the following function

locf2 <- function(x, initial=NA, IS_BAD = is.na) {
    # Replace 'bad' values in 'x' with last previous non-bad value.
    # If no previous non-bad value, replace with 'initial'.
    stopifnot(is.function(IS_BAD))
    good <- !IS_BAD(x)
    stopifnot(is.logical(good), length(good) == length(x), !anyNA(good))
    i <- cumsum(good)
    x <- x[c(1,which(good))][i+1]
    x[i==0] <- initial
    x
}

as in

> locf2(c("", "A", "B", "", "", "C", ""), IS_BAD=function(x)x=="", initial="---")
[1] "---" "A"   "B"   "B"   "B"   "C"   "C"
> locf2(factor(c(NA,"Small","Medium",NA,"Large",NA,NA,NA,"Small")))
[1] <NA>   Small  Medium Medium Large  Large  Large  Large  Small
Levels: Large Medium Small
> locf2(c(12, NA, 10, 11, NA, NA))
[1] 12 12 10 11 11 11

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Wed, Mar 15, 2017 at 4:08 AM, Allan Tanaka <allantanaka11 at yahoo.com> wrote:
> The following is an example:
>
> | Item_Identifier | Item_Weight |
> | FDP10 | 19 |
> | FDP10 |  |
> | DRI11 | 8.26 |
> | DRI11 |  |
> | FDW12 | 8.315 |
> | FDW12 |  |
>
>
> The following is the one that i want to be. That is, filling NA values from the previous Non-NA values.
> | Item_Identifier | Item_Weight |
> | FDP10 | 19 |
> | FDP10 | 19 |
> | DRI11 | 8.26 |
> | DRI11 | 8.26 |
> | FDW12 | 8.315 |
> | FDW12 | 8.315 |
>
>
> My current code data frame: train <- read.csv("Train.csv", header=T,sep = ",",na.strings = c(""," ",NA))
>
>
> Some people suggest to use na.locf function but in my case, i don't have numeric unique values in my Item_Identifier coloumn but rather it's characters. Not sure what to solve this problem.
>
>
>         [[alternative HTML version deleted]]
>
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