[R] merged data frame with <NA>

Tue Sep 29 10:09:53 CEST 2020

Hi Stefano,

For the merge() part, I'll leave it to more expert users (I rarely use 
merge(), and every time I need it, it's painful...).

To know why <NA> instead of NA, check the results with str(df3); I guess 
it is not the mode you expected.

For more details, you should provide the file, or better a reproducible 
example using dput().

For the second part, your syntax was not correct (subsetting a column 
for elements based on a column that is not part of the subset!). And 
there is no column "pch" in your example. Try:
df3[df3$event == "start", "event"] <- 24

HTH,
Ivan

--
Dr. Ivan Calandra
TraCEr, laboratory for Traceology and Controlled Experiments
MONREPOS Archaeological Research Centre and
Museum for Human Behavioural Evolution
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On 29/09/2020 9:59, Stefano Sofia wrote:
> Dear R users,
> I'm struggling with a simple "merge".
>
> I have an external file called df.txt like
>
> data_POSIX, event
> 2005-11-14 02:30:00, "start"
> 2005-11-14 11:30:00, "end"
>
> I load it with
>
> df1 <- read.table(file="df.txt", header=TRUE, sep=",", dec = ".", stringsAsFactors=FALSE)
> df1$data_POSIX <- as.POSIXct(df1$data_POSIX, format="%Y-%m-%d %H:%M:%S", tz="Etc/GMT-1")
>
> Then I create a new data frame df2:
>
> day_1 <- as.POSIXct("2005-11-14-00-00", format="%Y-%m-%d-%H-%M", tz="Etc/GMT-1")
> day_2 <- as.POSIXct("2005-11-14-12-00", format="%Y-%m-%d-%H-%M", tz="Etc/GMT-1")
> df2 <- data.frame(data_POSIX=seq(day_1, day_2, by="30 min"))
>
> Finally
>
> df3 <- merge(df2, df1, by=c("data_POSIX"), all.x=TRUE)
>
> gives
>
>             data_POSIX event
> 1  2005-11-14 00:00:00    <NA>
> 2  2005-11-14 00:30:00    <NA>
> 3  2005-11-14 01:00:00    <NA>
> 4  2005-11-14 01:30:00    <NA>
> 5  2005-11-14 02:00:00    <NA>
> 6  2005-11-14 02:30:00  start
> 7  2005-11-14 03:00:00    <NA>
> 8  2005-11-14 03:30:00    <NA>
> 9  2005-11-14 04:00:00    <NA>
> 10 2005-11-14 04:30:00    <NA>
> 11 2005-11-14 05:00:00    <NA>
> 12 2005-11-14 05:30:00    <NA>
> 13 2005-11-14 06:00:00    <NA>
> 14 2005-11-14 06:30:00    <NA>
> 15 2005-11-14 07:00:00    <NA>
> 16 2005-11-14 07:30:00    <NA>
> 17 2005-11-14 08:00:00    <NA>
> 18 2005-11-14 08:30:00    <NA>
> 19 2005-11-14 09:00:00    <NA>
> 20 2005-11-14 09:30:00    <NA>
> 21 2005-11-14 10:00:00    <NA>
> 22 2005-11-14 10:30:00    <NA>
> 23 2005-11-14 11:00:00    <NA>
> 24 2005-11-14 11:30:00    end
> 25 2005-11-14 12:00:00    <NA>
>
> Why there is <NA> instead of NA?
> And why
>
> df3$pch[df3$event == "start"] <- 24
>
> gives a whole column of NA and not 24 at row 6?
>
>
>           (oo)
> --oOO--( )--OOo----------------
> Stefano Sofia PhD
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