[R] incorrect number of levels

[David Winsemius]

On Oct 8, 2010, at 3:04 PM, Chagaris, Dave wrote:

> I have a data set 382 rows and  63 columns.  One of the columns is  
> bay, and there are 6 bays.  But, the number of levels for this  
> factor is 7 when it should be six because there is some 'blank'  
> level "".  When I subset for the blank level "", I get 0 rows.

How did you do the subset?

> What in my data could be causing this?  Thanks.
>
>>   dim(datmtx)
> [1] 382  63
>
>
>>     datmtx$bay
>  [1] TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB  
> TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB  
> TB TB TB TB TB TB
> [51] TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB  
> TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB  
> TB TB TB TB TB TB
> [101] TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB  
> TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB  
> TB HI TB HI TB TB
> [151] TB TB TB TB TB HI TB HI HI HI TB HI HI HI TB HI HI HI HI HI HI  
> HI HI TB TB TB TB CH CH TB CH CH CH CH CH CH CH CH CH CH TB TB CH CH  
> CH CH CH CH CH CH
> [201] CH CH CH CH CH CH CH CH CH CH CH CH CH CH CH CH CH CH CH CH TB  
> HI HI HI TB HI HI TB TB TB TB TB TB TB TB TB TB HI TB TB TB TB TB TB  
> TB TB TB TB TB TB
> [251] TB HI HI HI CH CH CH CH CH CH CH CH CH CH HI HI CH CH CH CH CH  
> CH CH CH CH CH CH CH TB TB TB TB TB TB TB TB TB TB CH CH AP AP AP AP  
> AP AP HI HI HI CH
> [301] CH CH CH AP AP TB TB AP AP AP AP AP AP SA BB BB TB TB TB TB AP  
> HI AP SA AP HI AP AP HI HI TB HI AP SA AP AP AP AP AP AP AP AP SA AP  
> AP SA AP AP AP SA
> [351] SA SA AP AP AP CH CH CH CH CH AP BB BB BB BB BB TB CH CH CH CH  
> CH CH CH CH CH CH CH CH CH CH CH
> Levels:  AP BB CH HI SA TB
>
>>    levels(datmtx$bay)
> [1] ""   "AP" "BB" "CH" "HI" "SA" "TB"

What do you get with:

which(!datmtx$bay %in% c( "AP", "BB", "CH", "HI," "SA", "TB") )

-- 
David.
>
>>    nlevels(datmtx$bay)
> [1] 7
>
> David Chagaris
> Associate Research Scientist
> Florida Fish and Wildlife Conservation Commission
> Florida Fish and Wildlife Research Institute
> 100 8th Ave SE
> St. Petersburg, FL  33701
> (727) 896-8626 ext. 4305
> (727) 893-1374 fax
>
>
> 	[[alternative HTML version deleted]]
>
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David Winsemius, MD
West Hartford, CT