[R] confusion about write.csv

[Jeff Newmiller]

Use write.table.

Write.csv follows a very specific definition for csv... one element of which is that it is not allowed to have a second header line after data lines. The only way for write.csv to enforce this is to disallow appending.

On June 4, 2020 6:34:14 PM PDT, Erin Hodgess <erinm.hodgess using gmail.com> wrote:
> Hello!
>
>Hope everyone is doing as well as possible.
>
>I have a question about write.csv.  I thought that the append argument
>would permit adding another data frame with the same column names.
>
>Here is my example:
>
> date1 <- as.Date("2020-03-09")
> wday <- weekdays(date1)
> x1 <- data.frame(date=date1,day=wday,lev=1:5,y=rnorm(5))
> x1
>        date    day lev           y
>1 2020-03-09 Monday   1 -0.09543049
>2 2020-03-09 Monday   2  0.53943428
>3 2020-03-09 Monday   3 -0.79224851
>4 2020-03-09 Monday   4  0.68168147
>5 2020-03-09 Monday   5 -1.02902897
> write.csv(file="test1.csv",x1,row.names=FALSE)
> date1 <- date1 + 1
> wday <- weekdays(date1)
> x2 <- data.frame(date=date1,day=wday,lev=1:5,y=rnorm(5))
> x2
>        date     day lev          y
>1 2020-03-10 Tuesday   1 -0.6648301
>2 2020-03-10 Tuesday   2 -0.1137580
>3 2020-03-10 Tuesday   3  1.6532675
>4 2020-03-10 Tuesday   4 -0.5845293
>5 2020-03-10 Tuesday   5  0.2849392
> write.csv(file="test1.csv",x2,row.names=FALSE,append=TRUE)
>Warning message:
>In write.csv(file = "test1.csv", x2, row.names = FALSE, append = TRUE)
>:
>  attempt to set 'append' ignored
>
>The values from x2 appear in the test1.csv file.
>
>What am I missing, please?
>
>Thanks,
>Erin
>
>
>Erin Hodgess, PhD
>mailto: erinm.hodgess using gmail.com
>
>	[[alternative HTML version deleted]]
>
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-- 
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