position {HH}

Find or assign the implied position for graphing the levels of a factor. A new class "positioned", which inherits from "ordered" and "factor", is defined.

Description

The default values for plotting a factor x are the integers 1:length(levels(x)). These functions provide a way of specifying alternate plotting locations for the levels.

Usage

position(x)

position(x) <- value

## S3 method for class 'positioned'
is.numeric(x, ...)
## S3 method for class 'positioned'
as.numeric(x, ...)
## S3 method for class 'positioned'
x[..., drop=FALSE]
## S3 method for class 'positioned'
is.na(x)
as.positioned(x)
as.position(x)
is.positioned(x)
positioned(x, ..., value)
## S3 method for class 'positioned'
print(x, ...)
## S3 method for class 'positioned'
unique(x, incomparables = FALSE, ...)
unpositioned(x, ...)

Arguments

x

numeric vector or factor

value

numerical values to be associated with levels(x). The length(value) must equal length(levels(as.factor(x))).

...

other arguments.

drop

See Extract.

incomparables

See unique.

Value

position(x) <- value first forces its argument to be an ordered factor and then assigns the value to the "position" attribute of the ordered factor. The result is assigned class "positioned" and returned.

position(x) returns the position values associated with levels(x). If x is a positioned factor, then the "position" attribute is returned. If x is a factor, then the integers 1:length(levels(x)) are returned. For anything else, as.numeric(x) is returned.

as.position(x) returns a numeric vector the length of the original vector. If x inherits from "factor", then the values in the vector are the values in position(x) subscripted by the levels of the factor. If x is numeric, then x itself is returned.

unpositioned(x) removes the "position" attribute and removes the "positioned" value from the the class of the object.

Author(s)

Richard M. Heiberger <[e-mail]>

See Also

panel.interaction2wt, factor.

Examples

## ordered with character levels defaults to
## integer position of specified levels
tmp <- ordered(c("mm","cm","m","m","mm","cm"),
               levels=c("mm","cm","m")) ## size order
tmp
as.numeric(tmp)
levels(tmp)
position(tmp)
as.position(tmp)
as.positioned(tmp)
positioned(tmp)
unpositioned(tmp)
unique(tmp)

## position is assigned to ordered in specified order
tmp <- ordered(c("cm","mm","m","m","mm","cm"),
               levels=c("mm","cm","m")) ## size order
levels(tmp)
position(tmp) <- c(-3, -2, 0) ## log10 assigned in size order
tmp
as.numeric(tmp)
levels(tmp)
position(tmp)
as.position(tmp)
as.positioned(tmp)
positioned(tmp)
unpositioned(tmp)
unique(tmp)

## numeric stays numeric
tmp <- c(0.010, 0.001, 1.000, 1.000, 0.001, 0.010)
tmp
as.numeric(tmp)
levels(tmp)
position(tmp)
as.position(tmp)
as.positioned(tmp)
positioned(tmp)
unpositioned(tmp)
unique(tmp)

## factor with numeric levels, position is integer position in size order
tmp <- factor(c(0.010, 0.001, 1.000, 1.000, 0.001, 0.010))
tmp
as.numeric(tmp)
levels(tmp)
position(tmp)
as.position(tmp)
as.positioned(tmp)
positioned(tmp)
unpositioned(tmp)
unique(tmp)

## ordered with numeric levels, position is numeric value in size order
tmp <- ordered(c(0.010, 0.001, 1.000, 1.000, 0.001, 0.010))
tmp
as.numeric(tmp)
levels(tmp)
position(tmp)
as.position(tmp)
as.positioned(tmp)
positioned(tmp)
unpositioned(tmp)
unique(tmp)


## factor with numeric levels
## position is assigned in size order
tmp <- factor(c(0.010, 0.001, 1.000, 1.000, 0.001, 0.010))
levels(tmp)
position(tmp) <- c(-3, -2, 0) ## log10 assigned in size order
tmp
as.numeric(tmp)
levels(tmp)
position(tmp)
as.position(tmp)
as.positioned(tmp)
positioned(tmp)
unpositioned(tmp)
unique(tmp)



## boxplots coded by week
tmp <- data.frame(Y=rnorm(40, rep(c(20,25,15,22), 10), 5),
                  week=ordered(rep(1:4, 10)))
position(tmp$week) <- c(1, 2, 4, 8)

bwplot(Y ~ week, horizontal=FALSE,
       scales=list(x=list(limits=c(0,9),
                          at=position(tmp$week),
                          labels=position(tmp$week))),
       data=tmp, panel=panel.bwplot.intermediate.hh)


#### You probably don't want to use the next two examples.
#### You need to be aware of their behavior.
##
## factor with character levels defaults to
## integer position of sorted levels.
## you probably DON'T want to do this!
tmp <- factor(c("cm","mm","m","m","mm","cm")) ## default alphabetic order
tmp
as.numeric(tmp)
levels(tmp)   ## you probably DON'T want to do this!
position(tmp) ## you probably DON'T want to do this!
as.numeric(tmp)
##
## position is assigned to factor in default alphabetic order.
## you probably DON'T want to do this!
tmp <- factor(c("cm","mm","m","m","mm","cm"))
levels(tmp)
position(tmp) <- c(-3, -2, 0) ## assigned in default alphabetic order
tmp
as.numeric(tmp)
levels(tmp)   ## you probably DON'T want to do this!
position(tmp) ## you probably DON'T want to do this!
as.numeric(tmp)