Re: [R] retaining formatting when converting a vector to amatrix/data.frame?

From: Bert Gunter <gunter.berton_at_gene.com>
Date: Thu, 3 Jan 2008 10:07:47 -0800

matrix() does not preserve class attributes, as it merely creates a matrix of mode the mode of its argument (possibly after some coercion), which is "numeric" for POSIXct, as you know.

So why not just manually set the class attribute after creation of the data.frame:

mydf <- data.frame(matrix(mydata,ncol=2)) for(i in seq(mydf))class(mydf[[i]]) <- class(mydata)

Cheers,

Bert Gunter
Genentech

-----Original Message-----
From: r-help-bounces_at_r-project.org [mailto:r-help-bounces_at_r-project.org] On Behalf Of Thomas Pujol
Sent: Thursday, January 03, 2008 9:02 AM To: r-help_at_stat.math.ethz.ch
Subject: [R] retaining formatting when converting a vector to amatrix/data.frame?

Please see example code below.    

  I have a vector ("mydata") of length 10. "mydata" can have various formats (e.g. numeric, text, POSIXct, etc) I use the matrix and data.frame functions to convert "mydata" to a dataframe ("mydf") of 2 columns and 5 rows.    

  What is a "good" way to ensure that the format is retained when I create the data.frame?
  Currently, data in the "POSIXct" format is converted to numeric.    

  Also, for my edification, is there a "good" way to convert numeric values such as these back to the original "POSIXct" format/values?    

  Much thanks!    

#here I lose the "POSIXct" formatting

  mydata <- rep(Sys.time(), 10)
  str(mydata)
  mydf <- data.frame(matrix(data=mydata, nrow=5, ncol=2)) str(mydf)    

#here using only "matrix" I also lose the "POSIXct" formatting

    mydata <- rep(Sys.time(), 10)
  str(mydata)
  mydf <- matrix(data=mydata, nrow=5, ncol=2) str(mydf)    

#this works as intended

  mydata <- rep(1:10)
  str(mydata)
  mydf <- data.frame(matrix(data=mydata, nrow=5, ncol=2)) str(mydf)        


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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. Received on Thu 03 Jan 2008 - 18:12:22 GMT

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