.-
help for ^logpred^
.-
Logistic regression probabilities (Joanne M. Garrett 05/08/98)
---------------------------------
^logpred^ yvar xvar [^if^ exp]^,^ [^f^rom^(^#^) t^o^(^#^) i^nc^(^#^) cl^ass^(^classvar^)^
^p^oly^(^#^) adj^ust^(^covlist^) m^odel ^gr^aph ^nol^ist
^l^evel^(^#^)^ graph_options]
^logpred^ calculates and prints probabilities and 95% confidence intervals from
logistic regression estimates for a continuous X variable, adjusted for
covariates. Default prints probabilities and confidence intervals; model
estimates and graph can be shown. Optionally a quadratic or a quadratic and
cubic term can be added to the model. An interaction between X and a nominal
variable can be estimated and graphed. Dummy variables are created for the
nominal variable with the lowest category defaulting to the reference group.
Variables and options required
------------------------------
yvar -- dependent variable (dichotomous 0,1)
xvar -- continuous independent variable (interval or ordinal)
^f^rom^(^#^)^ -- bottom value for xvar
^t^o^(^#^)^ -- top value for xvar
^i^nc^(^#^)^ -- increment size between bottom and top values (defaults to 1)
Options allowed
---------------
^cl^ass^(^classvar^)^ -- nominal variable for a xvar by classvar interaction
^p^oly^(^2 or 3^)^ -- polynomial terms added: 2=quadratic 3=quadratic and cubic
(will not work with the class option)
^adj^ust^(^covlist^)^ -- any covariates (if none specified, unadjusted
probabilities reported); Covariates set to their mean,
based on observations used in the analysis, or can be
set to user specified values (e.g., age=50 gender=1)
^m^odel -- displays the logistic regression table
^gr^aph -- displays graph of probabilities and 95% confidence intervals; if
class is requested, confidence intervals are not displayed
^nol^ist -- does not print list of probabilites and 95% CIs
^l^evel^(^#^)^ -- specifies the confidence level, in percent, for calculation
of confidence intervals (default=95%)
Examples
--------
. ^logpred died age, from(20) to(80) inc(5) adj(sys hra) model^
Calculates the probability of dying for 5 year increments of age
from 20 years to 80 years (i.e., age=20,25,30,...,80) adjusted
for systolic blood pressure and heart rate; displays model and
probabilites but does not display graph
. ^logpred died sys, f(60) t(300) i(20) adj(age hra) graph ylab xlab^
Calculates the probability of dying for systolic blood pressure
readings from 60 to 300 in 20 mm/hg increments, adjusted for age
and heart rate; displays graph and list of probabilites
. ^logpred died sys, f(60) t(300) i(20) adj(age hra) class(race) graph^
Calculates the probability of dying for systolic blood pressure
readings from 60 to 300 in 20 mm/hg increments, adjusted for age
and heart rate, by categories of race; displays a likelihood ratio
test for interaction; graphs the results
. ^logpred died age, f(40) t(80) poly(3) adj(sys=180) graph xlab ylab nolist^
Calculates the probability of dying for 1 year increments of age;
terms for age-squared and age-cubed included in model using the
poly(3) option; also adjusted for systolic blood pressure of 180;
displays graph; does not list probabilities and CIs