Help with Order

On 11/01/2010 7:37 AM, Steve Sidney wrote:

Dear List
As a fairly new R programmer I seem to have run into a strange  
problem - probably my inexperience with R
After reading and merging successive files into a single data  
frame, I find that order does not sort the data as expected.
I have multiple references in each file but each file refers to  
measurement data obtained at a different time.
Here's the code
library(reshape)
# Enter file name to Read & Save data
FileName=readline("Enter File name:\n")
# Find first occurance of file
for ( round1 in 1 : 6) {
ReadFile=paste(round1,"C_",FileName,"_Stats.csv", sep="")
if (file.exists(ReadFile))
break
}
x = data.frame(read.csv(ReadFile, header=TRUE),rnd=round1)
for ( round2 in (round1+1) : 6) {
#
ReadFile=paste(round2,"C_",FileName,"_Stats.csv", sep="")
if (file.exists(ReadFile)) {
y = data.frame(read.csv(ReadFile, header=TRUE),rnd = round2)
   if (round2 == (round1 +1))
   z=data.frame(merge(x,y,all=TRUE))
   z=data.frame(merge(y,z,all=TRUE))
}
}
ordered = order(z$lab_id)

results = z[ordered,]
res =  
data 
.frame 
( lab 
= 
results 
[,"lab_id 
"],bw=results[,"ZBW"],wi=results[,"ZWI"],pf_zbw=0,pf_zwi=0,r =  
results[,"rnd"])
#
# Establish no of samples recorded
nsmpls = length(res[,c("lab")])
# Evaluate Z_scores for Between Lab Results
for ( i in 1 : nsmpls) {
if (res[i,"bw"] > 3 | res[i,"bw"] < -3)
res[i,"pf_zbw"]=1
}
# Evaluate Z_scores for Within Lab Results
for ( i in 1 : nsmpls) {
if (res[i,"wi"] > 3 | res[i,"wi"] < -3)
res[i,"pf_zwi"]=1
}
dd = melt(res, id=c("lab","r"), "pf_zbw")
b = cast(dd, lab ~ r)
If anyone could see why the ordering only works for about 55 of 70  
records and could steer me in the right direction I would be obliged

I can't try out your code, but I'd guess it's due to conversion of  
strings to factors.  Sorting factors will sort them by their  
numerical value, not by the strings.

So the solution is to set stringsAsFactors=FALSE, either in each  
read.csv call, or globally with options(stringsAsFactors=FALSE).

Duncan Murdoch