Hi, I have a dataframe with many columns, including date and I want to keep only a few of the columns including date column. I used the following command: with(FireDataAppling, cbind(STARTDATE, County, TOTAL, CAUSE) It works, but the date becomes days from Jan 1, 2001. FireDataAppling$STARTDATE[1] gives [1] 2001-01-04 00:00:00 1703 Levels: ......... After the cbind command, the entry becomes a 4. I want to get 2001-01-04. What command should I use? Thank you. Daniel Chan Meteorologist Georgia Forestry Commission P O Box 819 Macon, GA 31202 Tel: 478-751-3508 Fax: 478-751-3465
Try
FireDataAppling[,c('STARTDATE','County','TOTAL','CAUSE')]
or perhaps the subset() function.
The way you are doing it is more complex than necessary (internally
complex, I mean, not how the code looks).
-Don
At 3:29 PM -0500 3/24/06, Dan Chan wrote:>Hi,
>
>I have a dataframe with many columns, including date and I want to keep
>only a few of the columns including date column.
>
>I used the following command:
>with(FireDataAppling, cbind(STARTDATE, County, TOTAL, CAUSE)
>
>It works, but the date becomes days from Jan 1, 2001.
>
>FireDataAppling$STARTDATE[1] gives
>[1] 2001-01-04 00:00:00
>1703 Levels: .........
>
>After the cbind command, the entry becomes a 4.
>
>I want to get 2001-01-04. What command should I use?
>
>Thank you.
>
>Daniel Chan
>Meteorologist
>Georgia Forestry Commission
>P O Box 819
>Macon, GA
>31202
>Tel: 478-751-3508
>Fax: 478-751-3465
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
--
--------------------------------------
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA
On Fri, 2006-03-24 at 15:29 -0500, Dan Chan wrote:> Hi, > > I have a dataframe with many columns, including date and I want to keep > only a few of the columns including date column. > > I used the following command: > with(FireDataAppling, cbind(STARTDATE, County, TOTAL, CAUSE) > > It works, but the date becomes days from Jan 1, 2001. > > FireDataAppling$STARTDATE[1] gives > [1] 2001-01-04 00:00:00 > 1703 Levels: .........This output suggests that STARTDATE is a factor, rather than a Date related data type. Did you read this data in via one of the read.table() family of functions? If these values are quoted character fields in the imported text file, they will be converted to factors by default.> After the cbind command, the entry becomes a 4. > > I want to get 2001-01-04. What command should I use? > > Thank you.You might want to review the "Note" section in ?cbind, relative to the result of cbind()ing vectors of differing data types. By using with(), you are effectively taking the data frame columns as individual vectors and the resultant _matrix_ will be coerced to a single data type, in this case, presumably numeric. I am guessing that 'County' and 'CAUSE' are also factors, whereas 'TOTAL' is numeric. Using str(FireDataAppling) will give you some insight into the structure of your data frame. The '4' that you are getting is the factor level numeric code for the entry above, not the number of days since Jan 1, 2001, which is not a default 'origin' date in R. Jan 1, 1970 is. You might want to look at ?factor for more insight here. If you want to retain only a _subset_ of the columns in a data frame, use the subset() function: subset(FireDataAppling, select = c(STARTDATE, County, TOTAL, CAUSE)) This will return a data frame and retain the original data types. If you want to then perform actual Date based operations on those values, take a look at ?DateTimeClasses, paying attention to the "See Also" section relative to associated functions. HTH, Marc Schwartz
Thank you Marc and Don's help, especially Marc's. Output<- subset(FireDataAppling, select = c(STARTDATE, County, TOTAL, CAUSE)) Worked! STARTDATE IS a factor and I used the following command to get the yyyy-mm-dd format of the date Output$Date<- as.POSIXct(Output$STARTDATE) Thank you! Daniel Chan -----Original Message----- From: Marc Schwartz (via MN) [mailto:mschwartz at mn.rr.com] Sent: Friday, March 24, 2006 9:22 PM To: Dan Chan Cc: r-help at stat.math.ethz.ch Subject: Re: [R] Date in dataframe manipulation On Fri, 2006-03-24 at 15:29 -0500, Dan Chan wrote:> Hi, > > I have a dataframe with many columns, including date and I want tokeep> only a few of the columns including date column. > > I used the following command: > with(FireDataAppling, cbind(STARTDATE, County, TOTAL, CAUSE) > > It works, but the date becomes days from Jan 1, 2001. > > FireDataAppling$STARTDATE[1] gives > [1] 2001-01-04 00:00:00 > 1703 Levels: .........This output suggests that STARTDATE is a factor, rather than a Date related data type. Did you read this data in via one of the read.table() family of functions? If these values are quoted character fields in the imported text file, they will be converted to factors by default.> After the cbind command, the entry becomes a 4. > > I want to get 2001-01-04. What command should I use? > > Thank you.You might want to review the "Note" section in ?cbind, relative to the result of cbind()ing vectors of differing data types. By using with(), you are effectively taking the data frame columns as individual vectors and the resultant _matrix_ will be coerced to a single data type, in this case, presumably numeric. I am guessing that 'County' and 'CAUSE' are also factors, whereas 'TOTAL' is numeric. Using str(FireDataAppling) will give you some insight into the structure of your data frame. The '4' that you are getting is the factor level numeric code for the entry above, not the number of days since Jan 1, 2001, which is not a default 'origin' date in R. Jan 1, 1970 is. You might want to look at ?factor for more insight here. If you want to retain only a _subset_ of the columns in a data frame, use the subset() function: subset(FireDataAppling, select = c(STARTDATE, County, TOTAL, CAUSE)) This will return a data frame and retain the original data types. If you want to then perform actual Date based operations on those values, take a look at ?DateTimeClasses, paying attention to the "See Also" section relative to associated functions. HTH, Marc Schwartz