R version 4.5.0 RC (2025-04-04 r88118 ucrt) -- "How About a Twenty-Six"
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Platform: x86_64-w64-mingw32/x64

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> library("zoo")

Attaching package: 'zoo'

The following objects are masked from 'package:base':

    as.Date, as.Date.numeric

> 
> x <- cbind(
+   c(1, NA, 2, NA, NA, NA, NA, 3),
+   c(NA, 1, NA, 2, NA, NA, NA, 3)
+ )
> na.locf(x)
     [,1] [,2]
[1,]    1   NA
[2,]    1    1
[3,]    2    1
[4,]    2    2
[5,]    2    2
[6,]    2    2
[7,]    2    2
[8,]    3    3
> na.locf(x, fromLast = TRUE)
     [,1] [,2]
[1,]    1    1
[2,]    2    1
[3,]    2    2
[4,]    3    2
[5,]    3    3
[6,]    3    3
[7,]    3    3
[8,]    3    3
> na.locf(x, maxgap = 3)
     [,1] [,2]
[1,]    1   NA
[2,]    1    1
[3,]    2    1
[4,]   NA    2
[5,]   NA    2
[6,]   NA    2
[7,]   NA    2
[8,]    3    3
> na.locf(x[,2])
[1] 1 1 2 2 2 2 3
> na.locf(x[,2], na.rm = FALSE)
[1] NA  1  1  2  2  2  2  3
> 
> z <- zoo(x, as.Date("2000-01-01") + 0:8)
> na.locf(z)
               
2000-01-01 1 NA
2000-01-02 1  1
2000-01-03 2  1
2000-01-04 2  2
2000-01-05 2  2
2000-01-06 2  2
2000-01-07 2  2
2000-01-08 3  3
2000-01-09 1  3
> na.locf(z, fromLast = TRUE)
               
2000-01-01 1  1
2000-01-02 2  1
2000-01-03 2  2
2000-01-04 3  2
2000-01-05 3  3
2000-01-06 3  3
2000-01-07 3  3
2000-01-08 3  3
2000-01-09 1 NA
> na.locf(z, maxgap = 3)
                
2000-01-01  1 NA
2000-01-02  1  1
2000-01-03  2  1
2000-01-04 NA  2
2000-01-05 NA  2
2000-01-06 NA  2
2000-01-07 NA  2
2000-01-08  3  3
2000-01-09  1  3
> na.locf(z[,2])
2000-01-02 2000-01-03 2000-01-04 2000-01-05 2000-01-06 2000-01-07 2000-01-08 
         1          1          2          2          2          2          3 
2000-01-09 
         3 
> na.locf(z[,2], na.rm = FALSE)
2000-01-01 2000-01-02 2000-01-03 2000-01-04 2000-01-05 2000-01-06 2000-01-07 
        NA          1          1          2          2          2          2 
2000-01-08 2000-01-09 
         3          3 
> 
> d <- as.Date("2000-01-01") + c(0, NA, 2, NA, NA, NA, NA, 7)
> na.locf(d)
[1] "2000-01-01" "2000-01-01" "2000-01-03" "2000-01-03" "2000-01-03"
[6] "2000-01-03" "2000-01-03" "2000-01-08"
> na.locf(d, fromLast = TRUE)
[1] "2000-01-01" "2000-01-03" "2000-01-03" "2000-01-08" "2000-01-08"
[6] "2000-01-08" "2000-01-08" "2000-01-08"
> na.locf(d, maxgap = 3)
[1] "2000-01-01" "2000-01-01" "2000-01-03" NA           NA          
[6] NA           NA           "2000-01-08"
> 
> proc.time()
   user  system elapsed 
   0.17    0.04    0.20