Date handling in R is hard to understand

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
project.org] On Behalf Of Alemu Tadesse
Sent: Friday, November 08, 2013 8:41 PM
To: r-help at r-project.org
Subject: [R] Date handling in R is hard to understand

Dear All,

I usually work with time series data. The data may come in AM/PM date
format or on 24 hour time basis. R can not recognize the two
differences automatically - at least for me. I have to specifically
tell R in which time format the data is. It seems that Pandas knows how
to handle date without being told the format. The problem arises when I
try to shift time by a certain time. Say adding 3600 to shift it
forward, that case I have to use something like:
Measured_data$Date <- as.POSIXct(as.character(Measured_data$Date),
tz="",format = "%m/%d/%Y %I:%M %p")+3600 or Measured_data$Date <-
as.POSIXct(as.character(Measured_data$Date),
tz="",format = "%m/%d/%Y %H:%M")+3600  depending on the format. The
date also attaches MDT or MST and so on. When merging two data frames
with dates of different format that may create a problem (I think).
When I get data from excel it could be in any/random format and I
needed to customize the date to use in R in one of the above formats.
Any TIPS - for automatic processing with no need to specifically tell
the data format ?

Another problem I saw was that when using r bind to bind data frames,
if one column of one of the data frames is a character data (say for
example none - coming from mysql) format R doesn't know how to
concatenate numeric column from the other data frame to it. I needed to

str(cbind(airquality, 1:153))

change the numeric to character and later after binding takes place I
had to re-convert it to numeric. But, this causes problem in an
automated environment. Any suggestion ?

Thanks
Mihretu

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