cstrata.psa: Supports Multiple Methods for Defining and Visualizing (PS)...

In PSAgraphics: Propensity Score Analysis Graphics

Supports Multiple Methods for Defining and Visualizing (PS) Strata

Description

Given propensity scores, allows strata to be directly user defined, possibly to: equalize sizes of strata, equalize the ranges of propensity scores, or to specify cut points on the unit interval. Once strata are created, a simple graphic is generated to visualize or judge strata for overlap and appropriateness. If a regression tree has been used, propensity scores are defined for each leaf of the tree.

Usage

cstrata.psa(
  treatment,
  propensity,
  strata = NULL,
  int = NULL,
  tree = FALSE,
  minsize = 2,
  graphic = TRUE,
  colors = c("dark blue", "dark green"),
  xlab = "Estimated Propensity Scores with Random Heights",
  pch = c(16, 16)
)

Arguments

treatment	Binary vector or factor defining the two treatments
propensity	Vector of same length as treatment containing estimated propensity scores.
strata	Either a vector of same length as treatment of predefined stratum number, or one integer n used to assign rows to n strata propensity scores, each of approximately the same number of cases. If relatively few unique propensity scores have been defined (as from a classification tree) then the logical tree should be set equal to TRUE.
int	Either a number m used to divide [0,1] into m equal length subintervals, or a vector containing cut points between 0 and 1 that define subintervals (perhaps as suggested by loess.psa). In either case the subintervals define strata, for which sizes can differ.
tree	Logical, default FALSE. If there are few unique propensity scores, say from a recursively partitioned tree, then TRUE forces strata to be defined by the unique propensity scores.
minsize	Smallest allowable stratum-treatment size. If violated, rows in the stratum are removed. User may wish to redefine strata.
graphic	Logical, default TRUE. If set to FALSE the graphic is not provided.
colors	2-ary color vector. Sets the colors of the points in the graphic. Default = c("blue", "orange")
xlab	Label for the x axis; default = "Estimated Propensity Scores with Random Heights".
pch	2-ary vector; determines the shape of points in the graphic. Default = c(16, 16).

Value

Original.Strata	Table of strata-treatment sizes before minsize evaluation.
Used.Strata	Table of strata-treatment sizes after minsize evaluation.
strata	Vector of the same length as treatment, indicating either the strata input by user or those created by the function.

Author(s)

James E. Helmreich [e-mail]

Robert M. Pruzek [e-mail]

KuangNan Xiong [e-mail]

See Also

cv.bal.psa, loess.psa

Examples

data(lindner)
attach(lindner)
lindner.ps <- glm(abcix ~ stent + height + female +
      diabetic + acutemi + ejecfrac + ves1proc,
      data = lindner, family = binomial)
ps <- lindner.ps$fitted
cstrata.psa(abcix, ps, strata = 5)
cstrata.psa(abcix, ps, strata = 10)
cstrata.psa(abcix, ps, int = c(.37, .56, .87, 1))

PSAgraphics documentation built on March 31, 2023, 5:30 p.m.