R help - Dec 2010 - Reorder factor and address embedded escapes

I am trying to reorder a factor variable that has embedded escape 
characters.  The data begins as a csv file with a factor that includes 
embedded new line characters.  By the time read.table has rendered it 
into a data frame, the variable now has an extra backslash.

e.g.
"This\nLabel" in the csv becomes "This\\nLabel" in the data
frame.

So, I am trying to reorder the factor and deal with the introduction of 
a secondary  \ .   Here's a small example:


A = c("A\\nB", "C\\nD")
test <-data.frame(A)
str(test)
test$reorderA <-factor(test$A, c("C\\nD", "A\\nB"))
str(test)
test$reorderB <-sub("\\\\n", "\n", test$reorderA)
str(test)

When sub is applied to the now-correctly ordered factor, it returns to 
the default ordering.

Suggestions?

Does the following help?

A = c("A\\nB", "C\\nD")
test <-data.frame(A)

#access levels directly to change names
levels(test$A) <- sub("\\\\n", "\n", levels(test$A))

#re-order levels of the factor
test$A <- relevel(test$A, "C\nD")


Rob James wrote:
> I am trying to reorder a factor variable that has embedded escape 
> characters.  The data begins as a csv file with a factor that includes 
> embedded new line characters.  By the time read.table has rendered it 
> into a data frame, the variable now has an extra backslash.
> 
> e.g.
> "This\nLabel" in the csv becomes "This\\nLabel" in the
data frame.
> 
> So, I am trying to reorder the factor and deal with the introduction of 
> a secondary  \ .   Here's a small example:
> 
> 
> A = c("A\\nB", "C\\nD")
> test <-data.frame(A)
> str(test)
> test$reorderA <-factor(test$A, c("C\\nD", "A\\nB"))
> str(test)
> test$reorderB <-sub("\\\\n", "\n", test$reorderA)
> str(test)
> 
> When sub is applied to the now-correctly ordered factor, it returns to 
> the default ordering.
> 
> Suggestions?
> 
> ______________________________________________
> R-help at r-project.org mailing list
> 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.

On Dec 10, 2010, at 3:14 PM, Rob James wrote:
> I am trying to reorder a factor variable that has embedded escape  
> characters.  The data begins as a csv file with a factor that  
> includes embedded new line characters.  By the time read.table has  
> rendered it into a data frame, the variable now has an extra  
> backslash.
>
> e.g.
> "This\nLabel" in the csv becomes "This\\nLabel" in the
data frame.
>
> So, I am trying to reorder the factor and deal with the introduction  
> of a secondary  \ .   Here's a small example:
>
>
> A = c("A\\nB", "C\\nD")
> test <-data.frame(A)
> str(test)
> test$reorderA <-factor(test$A, c("C\\nD", "A\\nB"))
> str(test)
> test$reorderB <-sub("\\\\n", "\n", test$reorderA)
> str(test)
>
> When sub is applied to the now-correctly ordered factor, it returns  
> to the default ordering.
Actually it returns a character vector rather than a factor.
>
> Suggestions?
Perhaps you should ask a question.

-- 
David Winsemius, MD
West Hartford, CT