glmChange2 {DAMisc}  R Documentation 
For objects of class glm
, it calculates the change in predicted
responses, for discrete changes in a covariate holding all other variables
at their observed values.
glmChange2(
obj,
varname,
data,
V = NULL,
diffchange = c("unit", "sd"),
outcome = c("diff", "maxdiff"),
baseline = c("obs", "median"),
catdiff = c("biggest", "all"),
n = 1,
R = 1500,
adjust = c("none", "shift", "trim"),
...
)
obj 
A model object of class 
varname 
Character string giving the variable name for which average effects are to be calculated. 
data 
Data frame used to fit 
V 
An optional variancecovariance matrix for the coefficients, if

diffchange 
A string indicating the difference in predictor values to
calculate the discrete change. 
outcome 
For quantitative variables, should the difference over the range of chosen values be calculated (the default) or should the maximum probability difference over the range be calculated. These will be the same for singleterm quantitative variables, but could be different for multiterm variables, like splines and polynomials. 
baseline 
Character string representing the baseline to use for the
change. It can be one of 
catdiff 
String identifying how differences in factor variables
is handled. Options are 
n 
Number of 
R 
Number of simulations to perform. 
adjust 
String identifying how range should be changed if it goes out of the bounds of the observed data. Trimming will simply truncate the size of the change to make it fit in bounds. Shifting will shift the interval so both ends are in bounds. If the shifted interval is wider than the range of the data, the change will be truncated to the range of the data. 
... 
Allows user to specify legacy argument 
The function calculates the average change in predicted probabiliy for a
discrete change in a single covariate with all other variables at their
observed values, for objects of class glm
. This function works with
polynomials specified with the poly
function.
res 
A vector of values giving the average and 95 percent confidence bounds 
ames 
The average change in predicted probability (across all N observations) for each of the R simulations. 
avesamp 
The average change in predicted probability for each of the N observation (across all of the R simulations). 
Dave Armstrong
data(france)
left.mod < glm(voteleft ~ male + age + retnat +
poly(lrself, 2), data=france, family=binomial)
glmChange2(left.mod, "age", data=france,
diffchange="sd")