Compute the basis of a clr-plane, to use with isometric log-ratio or planar transform of a (dataset of) compositions.
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optional dataset or vector of compositions
optional dataset or vector containing ilr or ipt coordinates
number of parts of the simplex
method to build the basis, one of "basic", "balanced", "optimal" "PBhclust", "PBmaxvar" or "PBangprox"
Method "basic" computes a triangular Helmert matrix (corresponding to
the original ilr transformation defined by Egozcue et al, 2003).
In this case,
ilrBase is a wrapper catching
the answers of
gsi.ilrBase and is to be
used as the more convenient function.
Method "balanced" returns an ilr matrix associated with a balanced partition,
splitting the parts in groups as equal as possible. Transforms
with this basis are less affected by any component (as happens with "basic").
The following methods are all data-driven and will fail if
x is not given.
Some of these methods are extended to non-acomp datasets via the
general functionality. Use with care with non-acomp objects!
Method "optimal" is a wrapper to
gsi.optimalilrBase, providing the ilr basis
with less influence of missing values. It is computed as a hierarchical
cluster of variables, with parts previously transformed to
1 (if the value is lost) or 0 (if it is recorded).
Methods "PBhclust", "PBmaxvar" and "PBangprox" are principal balance methods (i.e.
balances approximating principal components in different ways). These are all
resolved by calls to
gsi.PrinBal. Principal balances functionality should be
All methods give a matrix containing by columns the basis elements for the
canonical basis of the clr-plane used for the ilr and ipt transform. Only one of the
D is needed
to determine the dimension of the simplex.
Egozcue J.J., V. Pawlowsky-Glahn, G. Mateu-Figueras and
C. Barcel'o-Vidal (2003) Isometric logratio transformations for
compositional data analysis. Mathematical Geology, 35(3)
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