[R] How to order or sort a data.frame

[John Kane]

--- 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"

Thanks for helpl.

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




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>      
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http://www.student.kuleuven.be/~m0390867/dimitris.htm
> 
> 
> 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.
> >
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