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 <age...@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 <age...@meddatainc.com > >>> <mailto:age...@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()? > >>> > >>> ______________________________________________ > >>> R-help@r-project.org <mailto:R-help@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. > >>> > >> 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@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@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. ______________________________________________ R-help@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.
