probci {DAMisc}  R Documentation 
Calculates predicted probabilities for any combination of xvariable values holding all other variables constant at either typical values (average case approach) or at observed values (average effect approach).
probci(
obj,
data,
.b = NULL,
.vcov = NULL,
changeX = NULL,
numQuantVals = 5,
xvals = NULL,
type = c("aveEff", "aveCase"),
returnProbs = FALSE,
calcPW = FALSE
)
obj 
A model of class 
data 
Data frame used to estimate 
.b 
A vector of coefficients to be passed down to the simulation. If

.vcov 
A parameter variance covariance matrix to be passed to the
simulation. If 
changeX 
A vector of strings giving the names of variables for which changes are desired. 
numQuantVals 
For quantitative variables, if no xvalues are specified
in 
xvals 
A named list of values used to make the predictions. The names
in the list should correspond with the variable names specified in

type 
Type of effect to be generated. 
returnProbs 
Whether or not the vecot/matrix of predicted probabilities should be returned as well. 
calcPW 
Should the pairwise differences be calculated? 
Calculates predicted probabilities for any combination of xvariable values holding all other variables constant at either typical values (average case approach) or at observed values (average effect approach). The function uses a parametric bootstrap to provide generate confidence bounds for predicted probabilities and their differences. The confidence intervals produced are raw percentile interviews (at the 5% level).
An data frame with the following variables:
variables 
The
variables and the values at which they are held constant. For example,

pred_prob 
The difference in predicted
probability given the following change in 
lower, upper 
The lower and upper 95% confidence bounds. 
Dave Armstrong
data(france)
left.mod < glm(voteleft ~ male + age + retnat +
poly(lrself, 2, raw=TRUE), data=france, family=binomial)
out < probci(left.mod, france, changeX="retnat")
out
out2 < probci(left.mod, france, changeX="lrself",
xvals = list(lrself = c(1,10)))
out2
out3 < probci(left.mod, france, changeX=c("lrself", "retnat"),
xvals = list(lrself = c(1,10)))
out3