Missing Value

Missing Value

How do I replace NA values with zeros in R

> m <- matrix(sample(c(NA, 1:10), 100, replace = TRUE), 10)
> d <- as.data.frame(m)
   V1 V2 V3 V4 V5 V6 V7 V8 V9 V10
1   4  3 NA  3  7  6  6 10  6   5
2   9  8  9  5 10 NA  2  1  7   2
3   1  1  6  3  6 NA  1  4  1   6
4  NA  4 NA  7 10  2 NA  4  1   8
5   1  2  4 NA  2  6  2  6  7   4
6  NA  3 NA NA 10  2  1 10  8   4
7   4  4  9 10  9  8  9  4 10  NA
8   5  8  3  2  1  4  5  9  4   7
9   3  9 10  1  9  9 10  5  3   3
10  4  2  2  5 NA  9  7  2  5   5

> d[is.na(d)] <- 0

> d
   V1 V2 V3 V4 V5 V6 V7 V8 V9 V10
1   4  3  0  3  7  6  6 10  6   5
2   9  8  9  5 10  0  2  1  7   2
3   1  1  6  3  6  0  1  4  1   6
4   0  4  0  7 10  2  0  4  1   8
5   1  2  4  0  2  6  2  6  7   4
6   0  3  0  0 10  2  1 10  8   4
7   4  4  9 10  9  8  9  4 10   0
8   5  8  3  2  1  4  5  9  4   7
9   3  9 10  1  9  9 10  5  3   3
10  4  2  2  5  0  9  7  2  5   5

listwise deletion of missing values

# create new dataset without missing data 
newdata <- na.omit(mydata)

na.locf 함수 사용

zoo package에 구현되어 있는 함수이다.

Last Observation Carried Forward

Generic function for replacing each NA with the most recent non-NA prior to it.

x <- c(NA,NA, "A","A", "B","B","B", NA,NA, "C", NA,NA,NA, "A","A","B", NA,NA)
na.locf(x)
x

출력 결과

 [1] "A" "A" "B" "B" "B" "B" "B" "C" "C" "C" "C" "A" "A" "B" "B" "B"

참고 사이트: http://www.cookbook-r.com/Manipulating_data/Filling_in_NAs_with_last_non-NA_value/