filling specific column in a dataframe

Question

My data have this format and the frame named ex:

Day                  value1         value2
12-12-2012 00:00:00  1                 1
12-12-2012 00:00:02  NA                2
12-12-2012 00:00:03  1                 NA
12-12-2012 00:00:04  NA                4
12-12-2012 00:00:00  2                 1
12-12-2012 00:00:02  NA                2
12-12-2012 00:00:03  2                 NA
12-12-2012 00:00:04  NA                4

The output I want is:

Day                 value1         value2
12-12-2012 00:00:00  1                  1
12-12-2012 00:00:02  1                  2
12-12-2012 00:00:03  1                  NA
12-12-2012 00:00:04  1                  4
12-12-2012 00:00:00  2                  1
12-12-2012 00:00:02  2                  2
12-12-2012 00:00:03  2                  NA
12-12-2012 00:00:04  2                  4

What I tried:

fl = na.locf(ex$value1)

However the problem is that delete the value2. How can I use na.locf in a specific column in a frame with multiple columns with delete them?

Answer 1

require(zoo)

dat <- read.table(text="
Day                  value1         value2
12-12-2012 00:00:00  1                 1
12-12-2012 00:00:02  NA                2
12-12-2012 00:00:03  1                 NA
12-12-2012 00:00:04  NA                4
12-12-2012 00:00:00  2                 1
12-12-2012 00:00:02  NA                2
12-12-2012 00:00:03  2                 NA
12-12-2012 00:00:04  NA                4",header=TRUE, row.names=NULL)

dat$value1 <- na.locf(dat$value1)

Answer 2

I've tried to reproduce your problem, but for me you suggested solution works as you desire.

> require(zoo)
> ex <-data.frame(
    Day =c("12-12-2012 00:00:00","12-12-2012 00:00:02","12-12-2012 00:00:03","12-12-2012 00:00:04","12-12-2012 00:00:00","12-12-2012 00:00:02","12-12-2012 00:00:03","12-12-2012 00:00:04"), 
    value1 = c(1,NA,1,NA,2,NA,2,NA), 
    value2 = c(1,2,3,4,1,2,3,4))
> fl = na.locf(ex)
> fl
                  Day value1 value2
1 12-12-2012 00:00:00      1      1
2 12-12-2012 00:00:02      1      2
3 12-12-2012 00:00:03      1      3
4 12-12-2012 00:00:04      1      4
5 12-12-2012 00:00:00      2      1
6 12-12-2012 00:00:02      2      2
7 12-12-2012 00:00:03      2      3
8 12-12-2012 00:00:04      2      4

Perhaps something else is awry?