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

[Rui Barradas]

Hello,

The documentation says the following.

field.types
A list whose names are the column names and whose contents are the 
SQLite types (not the R class names) of the columns.


So argument field.types is a named list.

  - The list members names are the column names of the table to be read.
  - The list members values are SQLite types, like "CHAR", "VARCHAR", 
"INT", etc.


As for colClasses, those are R class names.

Rui Barradas




Às 17:59 de 18/07/2020, H escreveu:
> 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()?
>>>>
>>>>       ______________________________________________
>>>>       R-help using r-project.org <mailto:R-help using r-project.org> mailing list -- To UNSUBSCRIBE and more, see
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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.

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