R help - Jul 2018 - Read in data table, change columns from factors

On Wed, 18 Jul 2018, David Winsemius wrote:
> I would not destroy the possibility of using the original values:
David,

   What are the benefits of keeping date and time as factors?
>> allyears$myDate <- as.Date(as.character(allyears$date))
>> allyears$myTime <- as.POSIXct(paste(allyears$date, allyears$time))
   The latter command is not working on the full (402415 rows in the allyears
data set):

allyears$myTime <- as.POSIXct(paste(allyears$date, allyears$time))
Error in as.POSIXlt.character(x, tz, ...) :
   character string is not in a standard unambiguous format
> It's spelled `as.numeric`,
   Ah, I missed that. Thank you.
> ... but I'm having difficulty thinking about what sort of elevation (or
would
> that be "depth") would be be measured by
"-3762938880000000369098752".
   I also was curious about that figure and grep doesn't find it in the
original data file so I've no idea where R-3.5.0 came up with it.

   I'll read more about the POSIX datetime functions.

Thanks again,

Rich

> On Jul 18, 2018, at 4:07 PM, Rich Shepard <rshepard at
appl-ecosys.com> wrote:
> 
> On Wed, 18 Jul 2018, David Winsemius wrote:
> 
>> I would not destroy the possibility of using the original values:
> 
> David,
> 
>  What are the benefits of keeping date and time as factors?
> 
>>> allyears$myDate <- as.Date(as.character(allyears$date))
>>> allyears$myTime <- as.POSIXct(paste(allyears$date,
allyears$time))

It's not so much as factors but rather in a form that paste() will coerce to
character so you cna get the automatic format
> 
>  The latter command is not working on the full (402415 rows in the allyears
> data set):
> 
> allyears$myTime <- as.POSIXct(paste(allyears$date, allyears$time))
> Error in as.POSIXlt.character(x, tz, ...) :
>  character string is not in a standard unambiguous format
Maybe you need to add a format string. It might force some of your pasted
date+time values to NA but at least you would be able to identify the original
values and perhaps fix errors.

You really should include a large snapshot of data that will allow
reproducibility.

> 
>> It's spelled `as.numeric`,
> 
>  Ah, I missed that. Thank you.
> 
>> ... but I'm having difficulty thinking about what sort of elevation
(or would
>> that be "depth") would be be measured by
"-3762938880000000369098752".
> 
>  I also was curious about that figure and grep doesn't find it in the
> original data file so I've no idea where R-3.5.0 came up with it.
> 
>  I'll read more about the POSIX datetime functions.
> 
> Thanks again,
> 
> Rich
> 
> ______________________________________________
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> and provide commented, minimal, self-contained, reproducible code.
David Winsemius
Alameda, CA, USA

'Any technology distinguishable from magic is insufficiently advanced.' 
-Gehm's Corollary to Clarke's Third Law

On Wed, 18 Jul 2018, David Winsemius wrote:
> It's not so much as factors but rather in a form that paste() will
coerce
> to character so you cna get the automatic format
David,

   Now I understand.
> Maybe you need to add a format string. It might force some of your pasted
> date+time values to NA but at least you would be able to identify the
> original values and perhaps fix errors.
   Thinking about the data I realize that rather than separate date and time
columns what's needed is a datetime string. I'll add the format string
in
the morning and work on this.
> You really should include a large snapshot of data that will allow
> reproducibility.
   I'll certainly do this. With hourly and half-hourly data from 1989-June
2018 (but missing all of 1992) there are more than 400K rows in the raw data
file. If you would suggest how many would be an acceptably large number I'll
be happy to put that on a 'cloud' sharing site and provide the URL to
it.

Best regards,

Rich