idt | R Documentation |
Compute the isometric default transform of a vector (or dataset) of compositions or amounts in the selected class.
idt(x,...)
## Default S3 method:
idt( x,... )
## S3 method for class 'acomp'
idt( x ,...)
## S3 method for class 'rcomp'
idt( x ,...)
## S3 method for class 'aplus'
idt( x ,...)
## S3 method for class 'rplus'
idt( x ,...)
## S3 method for class 'rmult'
idt( x ,...)
## S3 method for class 'ccomp'
idt( x ,...)
## S3 method for class 'factor'
idt( x ,...)
## S3 method for class 'data.frame'
idt( x ,...)
idtInv(x,orig=gsi.orig(x),...)
## Default S3 method:
idtInv( x ,orig=gsi.orig(x),...)
## S3 method for class 'acomp'
idtInv( x ,orig=gsi.orig(x), V=gsi.getV(x),...)
## S3 method for class 'rcomp'
idtInv( x ,orig=gsi.orig(x), V=gsi.getV(x),...)
## S3 method for class 'aplus'
idtInv( x ,orig=gsi.orig(x),...)
## S3 method for class 'rplus'
idtInv( x ,orig=gsi.orig(x),...)
## S3 method for class 'ccomp'
idtInv( x ,orig=gsi.orig(x),...)
## S3 method for class 'rmult'
idtInv( x ,orig=gsi.orig(x),...)
## S3 method for class 'factor'
idtInv( x ,orig=gsi.orig(x), V=gsi.getV(x),...)
## S3 method for class 'data.frame'
idtInv( x , orig=gsi.orig(x), ...)
x |
a classed amount or composition, to be transformed with its
isometric default transform, or its inverse; in case of the method for |
... |
generic arguments past to underlying functions |
orig |
a compositional object which should be mimicked
by the inverse transformation. It is the generic
argument. Typically the |
V |
matrix of (transposed, inverted) logcontrasts;
together with |
The general idea of this package is to analyse the same data with
different geometric concepts, in a fashion as similar as possible. For each of the
four concepts there exists an isometric transform expressing the geometry
in a full-rank euclidean vector space. Such a transformation is computed
by idt
. For acomp
the transform is ilr
, for
rcomp
it is ipt
, for
aplus
it is ilt
, and for
rplus
it is iit
. Keep in mind that the
transform does not keep the variable names, since there is no guaranteed
one-to-one relation between the original parts and each transformed
variable.
The inverse idtInv
is intended to allow for an "easy" and automatic
back-transformation, without intervention of the user. The argument orig
(the one determining the behaviour of idtInv
as a generic function)
tells the function which back-transformation should be applied, and
gives the column names of orig
to the back-transformed
values of x
. Therefore, it is very conventient to give the original classed
data set used in the analysis as orig
.
A corresponding matrix of row-vectors containing the transforms. (Exception: idt.data.frame can return a data.frame if the input has no "origClass"-attribute)
R. Tolosana-Delgado, K.Gerald v.d. Boogaart http://www.stat.boogaart.de
van den Boogaart, K.G. and R. Tolosana-Delgado (2008) "compositions": a unified R package to analyze Compositional Data, Computers & Geosciences, 34 (4), pages 320-338, \Sexpr[results=rd]{tools:::Rd_expr_doi("10.1016/j.cageo.2006.11.017")}.
backtransform
, cdt
, ilr
, ipt
,
ilt
, cdtInv
, ilrInv
, iptInv
,
iltInv
, iitInv
## Not run:
# the idt is defined by
idt <- function(x) UseMethod("idt",x)
idt.default <- function(x) x
idt.acomp <- function(x) ilr(x)
idt.rcomp <- function(x) ipt(x)
idt.aplus <- ilt
idt.rplus <- iit
## End(Not run)
idt(acomp(1:5))
idt(rcomp(1:5))
data(Hydrochem)
x = Hydrochem[,c("Na","K","Mg","Ca")]
y = acomp(x)
z = idt(y)
y2 = idtInv(z,y)
par(mfrow=c(2,2))
for(i in 1:4){plot(y[,i],y2[,i])}
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