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 <[email protected]
> <mailto:[email protected]>> 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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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.
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