[R] Mode Vs Class

[Heinz Tuechler]

Congratulation Bill for this very clear and useful explanation.

Heinz

At 14:58 08.04.2008, Bill.Venables at csiro.au wrote:
>'mode' is a mutually exclusive classification of objects according to
>their basic structure.  The 'atomic' modes are numeric, complex,
>charcter and logical.  Recursive objects have modes such as 'list' or
>'function' or a few others.  An object has one and only one mode.
>
>'class' is a property assigned to an object that determines how generic
>functions operate with it.  It is not a mutually exclusive
>classification.  If an object has no specific class assigned to it, such
>as a simple numeric vector, it's class is usually the same as its mode,
>by convention.
>
>Changing the mode of an object is often called 'coercion'.  The mode of
>an object can change without necessarily changing the class.  e.g.
>
> > x <- 1:16
> > mode(x)
>[1] "numeric"
> > dim(x) <- c(4,4)
> > mode(x)
>[1] "numeric"
> > class(x)
>[1] "matrix"
> > is.numeric(x)
>[1] TRUE
> > mode(x) <- "character"
> > mode(x)
>[1] "character"
> > class(x)
>[1] "matrix"
>
>However:
>
> > x <- factor(x)
> > class(x)
>[1] "factor"
> > mode(x)
>[1] "numeric"
> >
>
>At this stage, even though x has mode numeric again, its new class,
>'factor', inhibits it being used in arithmetic operations.
>
>In practice, mode is not used very much, other than to define a class
>implicitly when no explicit class has been assigned.
>
>-----Original Message-----
>From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
>On Behalf Of Shubha Vishwanath Karanth
>Sent: Tuesday, 8 April 2008 10:20 PM
>To: r-help at stat.math.ethz.ch
>Subject: [R] Mode Vs Class
>
>Hi R,
>
>Just came across the 'mode' of an object. What is the basic difference
>between ?class and ?mode ... For example:
>
>d <- data.frame(a = c(1,2), b = c(5,6))
>
>class(d)
>
>[1] "data.frame"
>
>mode(d)
>
>[1] "list"
>
>But,
>
>c <- c(2,3,5,6,7)
>
>class(c)
>
>[1] "numeric"
>
>mode(c)
>
>[1] "numeric"
>
>Could anyone help me out...
>
>Thanks,
>
>shubha
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>______________________________________________
>R-help at r-project.org mailing list
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>PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.