factors in data.frames (PR#835)

Brian Ripley · 2001-02-01T10:15:26Z

> From: james.lindsey@luc.ac.be > Date: Thu, 1 Feb 2001 10:56:07 +0100 (MET) > > The following seems to be a contradiction: What is, pray? > class(df[, 1]) [1] "factor" > class(df[, 1, drop = FALSE]) [1] "data.frame" df[ , 1, drop=FALSE] is a data frame, so not a factor. df[ , 1] is a factor. > > df > df[,1] > [1] 1 2 1 2 1 2 1 2 1 2 > Levels: 1 2 > > df[,1,drop=F] > x > 1 1 > 2 2 > 3 1 > 4 2 > 5 1 > 6 2 > 7 1 > 8 2 > 9 1 > 10 2 > > is.factor(df[

Brian Ripley

Thu, Feb 1, 2001 2:15 AM

What is, pray?

[1] "factor"

[1] "data.frame"

df[ , 1, drop=FALSE] is a data frame, so not a factor.
df[ , 1] is a factor.

Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595


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