[R] Help with read.csv.sql()

[William Michels]

Do either of the postings/threads below help?

https://r.789695.n4.nabble.com/read-csv-sql-to-select-from-a-large-csv-file-td4650565.html#a4651534
https://r.789695.n4.nabble.com/using-sqldf-s-read-csv-sql-to-read-a-file-with-quot-NA-quot-for-missing-td4642327.html

Otherwise you can try reading through the FAQ on Github:

https://github.com/ggrothendieck/sqldf

HTH, Bill.

W. Michels, Ph.D.



On Sat, Jul 18, 2020 at 9:59 AM H <agents using meddatainc.com> wrote:
>
> On 07/18/2020 11:54 AM, Rui Barradas wrote:
> > Hello,
> >
> > I don't believe that what you are asking for is possible but like Bert suggested, you can do it after reading in the data.
> > You could write a convenience function to read the data, then change what you need to change.
> > Then the function would return this final object.
> >
> > Rui Barradas
> >
> > Às 16:43 de 18/07/2020, H escreveu:
> >
> >> On 07/17/2020 09:49 PM, Bert Gunter wrote:
> >>> Is there some reason that you can't make the changes to the data frame (column names, as.date(), ...) *after* you have read all your data in?
> >>>
> >>> Do all your csv files use the same names and date formats?
> >>>
> >>>
> >>> 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 Fri, Jul 17, 2020 at 6:28 PM H <agents using meddatainc.com <mailto:agents using meddatainc.com>> wrote:
> >>>
> >>>      I have created a dataframe with columns that are characters, integers and numeric and with column names assigned by me. I am using read.csv.sql() to read portions of a number of large csv files into this dataframe, each csv file having a header row with columb names.
> >>>
> >>>      The problem I am having is that the csv files have header rows with column names that are slightly different from the column names I have assigned in the dataframe and it seems that when I read the csv data into the dataframe, the column names from the csv file replace the column names I chose when creating the dataframe.
> >>>
> >>>      I have been unable to figure out if it is possible to assign column names of my choosing in the read.csv.sql() function? I have tried various variations but none seem to work. I tried colClasses = c(....) but that did not work, I tried field.types = c(...) but could not get that to work either.
> >>>
> >>>      It seems that the above should be feasible but I am missing something? Does anyone know?
> >>>
> >>>      A secondary issue is that the csv files have a column with a date in mm/dd/yyyy format that I would like to make into a Date type column in my dataframe. Again, I have been unable to find a way - if at all possible - to force a conversion into a Date format when importing into the dataframe. The best I have so far is to import is a character column and then use as.Date() to later force the conversion of the dataframe column.
> >>>
> >>>      Is it possible to do this when importing using read.csv.sql()?
> >>>
> >>>      ______________________________________________
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> >>>      PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> >>>      and provide commented, minimal, self-contained, reproducible code.
> >>>
> >> Yes, the files use the same column names and date format (at least as far as I know now.) I agree I could do it as you suggest above but from a purist perspective I would rather do it when importing the data using read.csv.sql(), particularly if column names and/or date format might change, or be different between different files. I am indeed selecting rows from a large number of csv files so this is entirely plausible.
> >>
> >> Has anyone been able to name columns in the read.csv.sql() call and/or force date format conversion in the call itself? The first refers to naming columns differently from what a header in the csv file may have.
> >>
> >>
> >>     [[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.
> >
> The documentation for read.csv.sql() suggests that colClasses() and/or field.types() should work but I may well have misunderstood the documentation, hence my question in this group.
>
> ______________________________________________
> 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.