fread doesn't check colClasses to be valid type

> sapply(fread("A,B\n1,2",colClasses="numeric"),class)   # ok
        A         B 
"numeric" "numeric" 
> sapply(fread("A,B\n1,2",colClasses="integer"),class)    # ok
        A         B 
"integer" "integer" 
> sapply(fread("A,B\n1,2",colClasses="string"),class)      # type "string" works?
          A           B 
"character" "character" 
> sapply(fread("A,B\n1,2",colClasses="c"),class)             
          A           B 
"character" "character" 
> sapply(fread("A,B\n1,2",colClasses="foo"),class)      # should be error that foo isn't valid type?
          A           B 
"character" "character" 
>

maybe just produce a warning for all of the above?

how exactly we want to define valid type?

Add tests for Rdatatable#1634

Check colClasses to be valid type. Closes Rdatatable#1634

@jangorecki

@jangorecki Looking at Hugh's PR #2545 made me realize the answer to your question. Just as read.csv, "foo" is a valid type to use in colClasses= if as.foo.character() or as.foo.default() exists. Otherwise, standard R error that as.foo method does not exist.

Whether as.* exists will be dependent on the local user's setup. I suppose this is a desired behavior -- users expecting coercion to foo class with methods defined in bar library can be trusted to handle loading bar themselves before running fread. From a glance at #2545, the backup (to use default interpretation, typically character) with a warning is probably ideal behavior -- if I forget to load bar, I'd rather be warned that the ex-post conversion was abandoned than to have fread fail.

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fread doesn't check colClasses to be valid type #1634

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fread doesn't check colClasses to be valid type #1634

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MichaelChirico commented on Apr 7, 2016

jangorecki commented on Jun 2, 2016

mattdowle commented on Jan 4, 2018

MichaelChirico commented on Jan 8, 2018

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