dissassoc: Analysis of discrepancy from dissimilarity measures

Description Usage Arguments Details Value Author(s) References See Also Examples

Description

Compute and test the share of discrepancy (defined from a dissimilarity matrix) explained by a categorical variable.

Usage

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dissassoc(diss, group, weights=NULL, R=1000,
          weight.permutation="replicate", squared=FALSE)

Arguments

diss

A dissimilarity matrix or a dist object (see dist)

group

A categorical variable. For a numerical variable use dissmfacw.

weights

optional numerical vector containing weights.

R

Number of permutations for computing the p-value. If equal to 1, no permutation test is performed.

weight.permutation

Weighted permutation method: "diss" (attach weights to the dissimilarity matrix), "replicate" (replicate case using weights), "rounded-replicate" (replicate case using rounded weights), "random-sampling" (random assignment of covariate profiles to the objects using distributions defined by the weights.)

squared

Logical. If TRUE the dissimilarities diss are squared.

Details

The dissassoc function assesses the association between objects characterized by their dissimilarity matrix and a discrete covariate. It provides a generalization of the ANOVA principle to any kind of distance metric. The function returns a pseudo R-square that can be interpreted as a usual R-square. The statistical significance of the association is computed by means of permutation tests. The function performs also a test of discrepancy homogeneity (equality of within variances) using a generalization of the Levene statistic and Bartlett's statistics.
There are print and hist methods (the latter producing an histogram of the permuted values used for testing the significance).

If a numeric group variable is provided, it will be treated as categorical, i.e., each different value will be considered as a different category. To measure the ‘linear’ effect of a numerical variable, use dissmfacw.

Value

An object of class dissassoc with the following components:

groups

A data frame with the number of cases and the discrepancy of each group

anova.table

The pseudo ANOVA table

stat

The value of the statistics and their p-values

perms

The permutation object, containing the values computed for each permutation

Author(s)

Matthias Studer (with Gilbert Ritschard for the help page)

References

Studer, M., G. Ritschard, A. Gabadinho and N. S. Müller (2011). Discrepancy analysis of state sequences, Sociological Methods and Research, Vol. 40(3), 471-510.

Studer, M., G. Ritschard, A. Gabadinho and N. S. Müller (2010) Discrepancy analysis of complex objects using dissimilarities. In F. Guillet, G. Ritschard, H. Briand, and D. A. Zighed (Eds.), Advances in Knowledge Discovery and Management, Studies in Computational Intelligence, Volume 292, pp. 3-19. Berlin: Springer.

Studer, M., G. Ritschard, A. Gabadinho and N. S. Müller (2009). Analyse de dissimilarités par arbre d'induction. In EGC 2009, Revue des Nouvelles Technologies de l'Information, Vol. E-15, pp. 7–18.

Anderson, M. J. (2001) A new method for non-parametric multivariate analysis of variance. Austral Ecology 26, 32–46.

Batagelj, V. (1988) Generalized Ward and related clustering problems. In H. Bock (Ed.), Classification and related methods of data analysis, Amsterdam: North-Holland, pp. 67–74.

See Also

dissvar to compute the pseudo variance from dissimilarities and for a basic introduction to concepts of pseudo variance analysis.
disstree for an induction tree analyse of objects characterized by a dissimilarity matrix.
disscenter to compute the distance of each object to its group center from pairwise dissimilarities.
dissmfacw to perform multi-factor analysis of variance from pairwise dissimilarities.

Examples

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## Defining a state sequence object
data(mvad)
mvad.seq <- seqdef(mvad[, 17:86])

## Building dissimilarities (any dissimilarity measure can be used)
mvad.ham <- seqdist(mvad.seq, method="HAM")

## R=1 implies no permutation test
da <- dissassoc(mvad.ham, group=mvad$gcse5eq, R=10)
print(da)
hist(da)


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