How to order or sort a data.frame

Quoting John Kane <jrkrideau at yahoo.ca>:

--- Dimitrios Rizopoulos
<Dimitris.Rizopoulos at med.kuleuven.be> wrote:

try the following:

mdf <- data.frame(us.state, count, year, month)
mdf[order(mdf$year, mdf$month), ]

Thansk to Dimitris and Dieter. This has helped

since

seems to have shown me a way around the problem.

It

just means that I have to sort the data earlier.

What my example did not show clearly is that when

I

subset the data the variable 'month' which is

numeric

in the original dataframe becomes a factor.  I was
wondering if there was a way to sort the factor so
that I would get a numeric sort.  So far I have

not

been able to see how to coerce the factor "month"

into

a numeric when using 'order"

for converting factors to numeric check R FAQ 7.10.

Best,
Dimitris

Thanks for helpl.

Hi Hadley,
I have not had time to check out the reshape but
thanks.

Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/

Quoting John Kane <jrkrideau at yahoo.ca>:

I have a dataframe where I would like to order

first

by  variable, year, and then within that

variable

by

month.

So far the only way that I have seen to do this

is

to

order by year and then subset year and sort by

month

and then do an rbind to get things back

together.

Is this the right approach?

Example:

us.state <-rep("California", 23)

count <-

c(774,283,774,283,508,283,774,283,602,283,

774,508,0,602,330,283,283,283,602,301,126,

NA,301)

year <- c(2002,  2003, 2001, 2002, 2001, 2002,

2001,

2002, 2002, 2003,
          2002, 2002, 2001,  2002, 2001, 2002,

2001,

2002, 2001, 2002,
          2001, 2001, 2002)

month <- c( 1, 1, 10, 10, 11, 11, 12, 12,

            2, 2, 3, 4, 5, 5, 6, 6, 7, 7, 8, 8,

9,

9,

9)




df <- data.frame (cbind(us.state,count, year,

month))

# ordering as a factor works here

df1 <- df[order(df$year),]

df1



df2 <- subset(df1, year==2001)



# ordering as a factor works but not a good
appearance.


df3 <- df2[order(as.numeric(df2$month)),]

df3



This works but  "month" is ordered as  a factor

and I

would prefer to coerce it into a numeric for
presentation purposes but
 df3 <- df2[order(as.numeric(df2$month)),] does

not

seem to work,  nor has a couple of other things

I've

tried.

Any suggestions gratefully received.