[R] error message from read.csv in loop

[Bert Gunter]

"It seems that your problem is that you are using single quotes inside of
the double quotes."

That is FALSE. From ?Quotes:
"Single and double quotes delimit character constants. They can be
used interchangeably but double quotes are preferred (and character
constants are printed using double quotes), so single quotes are
normally only used to delimit character constants containing double
quotes."

Of course, pairs of each type of quote must properly match, must not
get confused with quotes in the delineated string, etc. , but they are
otherwise interchangeable. The whole of ?Quotes, especially the
examples, is informative and worth the read (imo).

Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Sat, Jul 10, 2021 at 8:20 AM Migdonio González
<migdonio.gonzalez02 using gmail.com> wrote:
>
>  It seems that your problem is that you are using single quotes inside of
> the double quotes. This is not necessary. Here is the corrected for-loop:
>
> for (j in 1:nrow(ora))
> {
>         mycol  <- ora[j,"fname"]
>         mycsv  <- paste0(mycol,".csv")
>         rdcsv  <- noquote(paste0("w:/project/_Joe.B/Oracle/data/", mycsv))
>         rr     <- read.csv(rdcsv)
> }
>
> Also note that the rr variable will only store the last CSV, not all CSV.
> You will need to initialize the rr variable as a list to store all CSVs if
> that is what you require. Something like this:
>
> # Initialize the rr variable as a list.
> rr <- as.list(rep(NA, nrow(ora)))
>
> # Run the for-loop to store all the CSVs in rr.
> for (j in 1:nrow(ora))
> {
>         mycol  <- ora[j,"fname"]
>         mycsv  <- paste0(mycol,".csv")
>         rdcsv  <- noquote(paste0("w:/project/_Joe.B/Oracle/data/", mycsv))
>         rr[[j]]     <- read.csv(rdcsv)
> }
>
> Regards
> Migdonio G.
>
> On Fri, Jul 9, 2021 at 1:10 PM Kai Yang via R-help <r-help using r-project.org>
> wrote:
>
> > Hello List,
> > I use for loop to read csv difference file into data frame rr.  The data
> > frame rr will be deleted after a comparison and go to the next csv file.
> > Below is my code:
> > for (j in 1:nrow(ora))
> > {
> >   mycol  <- ora[j,"fname"]
> >   mycsv  <- paste0(mycol,".csv'")
> >   rdcsv  <- noquote(paste0("'w:/project/_Joe.B/Oracle/data/", mycsv))
> >   rr     <- read.csv(rdcsv)
> > }
> > but when I run this code, I got error message below:
> > Error in file(file, "rt") : cannot open the connection
> > In addition: Warning message:
> > In file(file, "rt") :
> >   cannot open file
> > ''w:/project/_Joe.B/Oracle/data/ASSAY_DEFINITIONS.csv'': No such file or
> > directory
> >
> > so, I checked the rdcsv and print it out, see below:
> > [1] 'w:/project/_Joe.B/Oracle/data/ASSAY_DEFINITIONS.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/ASSAY_DISCRETE_VALUES.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/ASSAY_QUESTIONS.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/ASSAY_RUNS.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/DATA_ENTRY_PAGES.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/DISCRETE_VALUES.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/ENTRY_GROUPS.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/GEMD_CODELIST_GROUPS.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/GEMD_CODELIST_VALUES.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/GEMD_LOT_DEFINITIONS.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/GEMD_SAMPLES.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/MOLECULAR_WAREHOUSE.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/QUESTION_DEFINITIONS.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/QUESTION_GROUPS.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/RESPONDENTS.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/RESPONSES.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/SAMPLE_LIST.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/SAMPLE_LIST_NAMES.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/SAMPLE_PLATE_ADDRESSES.csv'
> > [1] 'w:/project/_Joe.B/Oracle/data/STORAGE_UNITS.csv'
> > it seems correct. I copy and paste it into a code :
> >  rr     <- read.csv( 'w:/project/_Joe.B/Oracle/data/RESPONDENTS.csv')
> > and it works fine.
> > Can someone help me debug where is the problem in my for loop code?
> > Thanks,
> > Kai
> >
> >
> >
> >
> >
> >         [[alternative HTML version deleted]]
> >
> > ______________________________________________
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> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.