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

Sun May 8 17:23:27 CEST 2005

```Hello,

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

Bruno

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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
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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?

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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