R help - Dec 2007 - Ordering the levels of a vector

Hi,

   I have a vector in a data frame that looks
something like this:

day<-c('Day -1','Day 6','Day 10')


   This vector specifies the order in which several
panel will appear in a lattice plots. But the order in
which such plots will appear will be the following:
Day -1, Day 10, Day 6. Which makes sense, but I cannot
name the Days like this: Day -01,Day 10, Day 06, which
would put the levels in the order I want them to be.

  Now, this vector won't always have the same values,
it could be:

day<-c('Day -1, 'Day 2','Day 14')

   So I cannot set the levels manually:

levels(day)<-c('Day -1', 'Day something','Day
something else')
 I tried as.ordered, but I guess I am not using the
right function. 

How can I command the script to put the panels in the
original  order given of the vector in a data frame?

Thank  you,

Judith








     
____________________________________________________________________________________
Be a better friend, newshound, and

Try mixedsort in the gtools package.

On Dec 3, 2007 4:21 PM, Judith Flores <juryef at yahoo.com>
wrote:
> Hi,
>
>   I have a vector in a data frame that looks
> something like this:
>
> day<-c('Day -1','Day 6','Day 10')
>
>
>   This vector specifies the order in which several
> panel will appear in a lattice plots. But the order in
> which such plots will appear will be the following:
> Day -1, Day 10, Day 6. Which makes sense, but I cannot
> name the Days like this: Day -01,Day 10, Day 06, which
> would put the levels in the order I want them to be.
>
>  Now, this vector won't always have the same values,
> it could be:
>
> day<-c('Day -1, 'Day 2','Day 14')
>
>   So I cannot set the levels manually:
>
> levels(day)<-c('Day -1', 'Day something','Day
> something else')
>  I tried as.ordered, but I guess I am not using the
> right function.
>
> How can I command the script to put the panels in the
> original  order given of the vector in a data frame?
>
> Thank  you,
>
> Judith
>
>
>
>
>
>
>
>
>     
____________________________________________________________________________________
> Be a better friend, newshound, and
>
> ______________________________________________
> 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 12/3/07, Judith Flores <juryef at yahoo.com>
wrote:
> Hi,
>
>    I have a vector in a data frame that looks
> something like this:
>
> day<-c('Day -1','Day 6','Day 10')
>
>
>    This vector specifies the order in which several
> panel will appear in a lattice plots. But the order in
> which such plots will appear will be the following:
> Day -1, Day 10, Day 6. Which makes sense, but I cannot
> name the Days like this: Day -01,Day 10, Day 06, which
> would put the levels in the order I want them to be.
>
>   Now, this vector won't always have the same values,
> it could be:
>
> day<-c('Day -1, 'Day 2','Day 14')
>
>    So I cannot set the levels manually:
>
> levels(day)<-c('Day -1', 'Day something','Day
> something else')
Well, you need some sort of rule that can be used to determine the
order of the levels. The default (see ?factor) is 'levels
sort(unique(x))'. If you instead want, say, levels in the order of
first appearance (assuming that's what you mean by "original
order"),
you could define

my.factor = function(x) { factor(x, levels = unique(x)) }

and then use
> day<- my.factor(c('Day -1','Day 6','Day 10'))
> day
[1] Day -1 Day 6  Day 10
Levels: Day -1 Day 6 Day 10
>  I tried as.ordered, but I guess I am not using the
> right function.
>
> How can I command the script to put the panels in the
> original  order given of the vector in a data frame?
-Deepayan

On Mon, 2007-12-03 at 13:21 -0800, Judith Flores wrote:
> Hi,
> 
>    I have a vector in a data frame that looks
> something like this:
> 
> day<-c('Day -1','Day 6','Day 10')
> 
> 
>    This vector specifies the order in which several
> panel will appear in a lattice plots. But the order in
> which such plots will appear will be the following:
> Day -1, Day 10, Day 6. Which makes sense, but I cannot
> name the Days like this: Day -01,Day 10, Day 06, which
> would put the levels in the order I want them to be.
> 
>   Now, this vector won't always have the same values,
> it could be:
> 
> day<-c('Day -1, 'Day 2','Day 14')
> 
>    So I cannot set the levels manually:
> 
> levels(day)<-c('Day -1', 'Day something','Day
> something else')
>  I tried as.ordered, but I guess I am not using the
> right function. 
> 
> How can I command the script to put the panels in the
> original  order given of the vector in a data frame?
> 
> Thank  you,
> 
> Judith
You could strip the 'Day' part of the elements using gsub(), sort the
numeric part and then paste() 'Day' back to the result:

set.seed(1)
day <- paste("Day", sample(-2:10))
> day
 [1] "Day 1"  "Day 2"  "Day 4"  "Day 7" 
"Day -1" "Day 5"  "Day 8"
 [8] "Day 10" "Day 3"  "Day -2" "Day 9" 
"Day 0"  "Day 6"

day.tmp <- sort(as.numeric(gsub("[^0-9\\-]", "", day)))
> day.tmp
 [1] -2 -1  0  1  2  3  4  5  6  7  8  9 10

day.levels <- paste("Day", day.tmp)
> day.levels
 [1] "Day -2" "Day -1" "Day 0"  "Day 1" 
"Day 2"  "Day 3"  "Day 4"
 [8] "Day 5"  "Day 6"  "Day 7"  "Day 8" 
"Day 9"  "Day 10"

day.ord <- factor(day, levels = day.levels)

# Note the order of the levels versus the order of the factor
output
> day.ord
 [1] Day 1  Day 2  Day 4  Day 7  Day -1 Day 5  Day 8  Day 10 Day 3 
[10] Day -2 Day 9  Day 0  Day 6 
13 Levels: Day -2 Day -1 Day 0 Day 1 Day 2 Day 3 Day 4 Day 5 ... Day 10


HTH,

Marc Schwartz