[R] Need a factor level even though there are no observations

[falissard]

Hello,

Does this work?
m <- as.factor(education.man)
levels(m)[1:3] <- factorlabels
table(m)

Bruno

----------------------------------------------------------------------------
Bruno Falissard
INSERM U669, PSIGIAM
"Paris Sud Innovation Group in Adolescent Mental Health"
Maison de Solenn
97 Boulevard de Port Royal
75679 Paris cedex 14, France
tel : (+33) 6 81 82 70 76
fax : (+33) 1 45 59 34 18
web site : http://perso.wanadoo.fr/bruno.falissard/
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-----Message d'origine-----
De : r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] De la part de Ajay Narottam Shah
Envoyé : dimanche 8 mai 2005 15:57
À : r-help
Objet : [R] Need a factor level even though there are no observations

I'm in this situation:

     factorlabels <- c("School", "College", "Beyond")

with data for 8 families:

     education.man  <- c(1,2,1,2,1,2,1,2)       # Note : no "3" values
     education.wife <- c(1,2,3,1,2,3,1,2)       # 1,2,3 are all present.

My goal is to create this table:

                     School     College      Beyond
       Husband       4          4            0
       Wife          3          3            2


How do I do this?

I can readily do:
     education.wife <- factor(education.wife, labels=factorlabels)

But this breaks:
     education.man <- factor(education.man,   labels=factorlabels)

because none of the families have a husband who went beyond college.

I get around this problem in a limited way by:
     cautiously <- function(x, labels) {
       factor(x, labels=factorlabels[as.numeric(levels(factor(x)))])
     }
     education.man <- cautiously(education.man, labels=factorlabels)

Now I get:

     > table(education.man)
     School College 
          4       4 
     > table(education.wife)
     School College  Beyond 
          3       3       2 

This is a pain because now the two tables are not conformable. How do
I get to my end goal, which is the table:

                     School     College      Beyond
       Husband       4          4            0
       Wife          3          3            2

In other words, how do I force education.man to have a factor with 3
levels - "School" "College" "Beyond" - even though there is no
observation in "Beyond".

-- 
Ajay Shah                                                   Consultant
ajayshah at mayin.org                      Department of Economic Affairs
http://www.mayin.org/ajayshah           Ministry of Finance, New Delhi

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