[R] Still missing something on missing values...

[Matej Cepl]

Hi,

I have a SPSS datafile which is used for my textbook in the
statistics (and which is available on
http://abacon.com/fox/s6720p2.sav, but it is originally from
ICPSR).

When I opened it with SPSS 10 and run Frequencies on it I 
have got 979 valid data a 27 missing. However, see below 
(unfortunately, I have used R in preparation of my homework, 
which caused me an error on this):

	> data=read.spss("s6720p2.sav")
	> levels(data$CP1)
	[1] "Rf"      "Dk"      "Neither" "Oppose"  "Favor"
	> length(data$CP1[data$CP1=="Favor"])
	[1] 727
	> length(data$CP1[data$CP1=="Oppose"])
	[1] 177
	> length(data$CP1[data$CP1=="Neither"])
	[1] 79
	> length(data$CP1[data$CP1=="Dk"])
	[1] 19
	> length(data$CP1[data$CP1=="Rf"])
	[1] 3
	> data$CP1[data$CP1=="Rf" | data$CP1=="Dk"]<-NA
	> length(data$CP1[!is.na(data$CP1)])
	[1] 983
	> length(data$CP1[is.na(data$CP1)])
	[1] 22
	> 727+177+79
	[1] 983

Now, what is even more strange is, that when I have exported just 
the variable CP1 from the full file (in SPSS) and run on it the 
same frequencies as in the full size version, the results were 
same as in R (yes, I have checked that the definition of the 
missing values was the same: 8,9 -- labelled as Rf and Dk).

I have uploaded the data and all reports (in PDF) on 
http://www.volny.cz/cepls/ps-pdf/s6720p2.zip.

Could anybody help me to understand what I did wrong, please?

	Thanks
	
		Matej

-- 
Matej Cepl, matej at ceplovi.cz, PGP ID# D96484AC
138 Highland Ave. #10, Somerville, Ma 02143, (617) 623-1488
 
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