LCcluster | R Documentation |
Form the full, hierarchical clustering tree (dendrogram) for all units (regardless of Treatment/Exposure status) using Mahalonobis distances computed from specified baseline X-covariate characteristics.
LCcluster(dframe, xvars, method="ward.D")
dframe |
Name of data.frame containing baseline X covariates. |
xvars |
List of names of X variable(s). |
method |
Hierarchical Clustering Method of "diana", "ward.D", "ward.D2", "complete", "average", "mcquitty", "median" or "centroid". |
The first step in applying Local Control Strategy to data is to hierarchically cluster experimental units in baseline X-covariate space ...thereby creating "Blocks" of relatively well-matched units. LCcluster first calls stats::prcomp() to calculate Mahalanobis distances using standardized and orthogonal Principal Coordinates. LCcluster then uses either the divisive cluster::diana() method or one of seven agglomerative methods from stats::hclust() to compute a dendrogram tree. The hclust function is based on Fortran code contributed to STATLIB by F. Murtagh.
An output list object of class LCcluster, derived from cluster::diana or stats::hclust.
dframe |
Name of data.frame containing all baseline X-covariates. |
xvars |
List of 1 or more X-variable names. |
method |
Hierarchical Clustering Method: "diana", "ward.D", "ward.D2", "complete", "average", "mcquitty", "median" or "centroid". |
hclobj |
Hierarchical clustering object created by the designated method. |
Bob Obenchain <wizbob@att.net>
Kaufman L, Rousseeuw PJ. (1990) Finding Groups in Data. An Introduction to Cluster Analysis. New York: John Wiley and Sons.
Kereiakes DJ, Obenchain RL, Barber BL, et al. (2000) Abciximab provides cost effective survival advantage in high volume interventional practice. Am Heart J 140: 603-610.
Murtagh F. (1985) Multidimensional Clustering Algorithms. COMPSTAT Lectures 4.
Obenchain RL. (2010) Local Control Approach using JMP. Chapter 7 of Analysis of Observational Health Care Data using SAS, Cary, NC:SAS Press, pages 151-192.
Rubin DB. (1980) Bias reduction using Mahalanobis metric matching. Biometrics 36: 293-298.
LCsetup
, ltdagg
and lrcagg
.
data(radon) xvars <- c("obesity", "over65", "cursmoke") hclobj <- LCcluster(radon, xvars) # ...using default method = "ward.D" plot(hclobj)
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