This is a special R-only entry.In Example 8.7, we showed the Hosmer and Lemeshow goodness-of-fit test. Today we demonstrate more advanced computational approaches for the test.If you write a function for your own use, it hardly matters what it looks l...
Blog Archives
Example 8.7: Hosmer and Lemeshow goodness-of-fit
The Hosmer and Lemeshow goodness of fit (GOF) test is a way to assess whether there is evidence for lack of fit in a logistic regression model. Simply put, the test compares the expected and observed number of events in bins defined by the predicted p...
Example 8.6: Changing the reference category for categorical variables
How can we change the reference category for a categorical variable? This question comes up often in a consulting practice.When including categorical covariates in regression models, there is a question of how to incorporate the categories. One simpl...
Example 8.5: bubble plots part 3
An anonymous commenter expressed a desire to see how one might use SAS to draw a bubble plot with bubbles in three colors, corresponding to a fourth variable in the data set. (x, y, z for bubble size, and the category variable.) In a previous entries...
Example 8.4: Including subsetting conditions in output
A number of analyses perform operations on subsets. Making it clear what observations have been excluded or included is helpful to include in the output.SASThe where statement (section A.6.3) is a powerful and useful tool for subsetting on the fly. (...
Summer hiatus
We're taking a break from posting for most of August. We'll be back in a month with new examples, including R- and SAS-applicable tricks and tools.Please drop us any ideas in the comments or by e-mail. We love feedback of any kind.
Example 8.2: Digits of Pi, redux
In example 8.1, we considered some simple tests for the randomness of the digits of Pi. Here we develop a different test and implement it. If each digit appears in each place with equal and independent probability, then the places between recurrences...
Example 8.1: Digits of Pi
Do the digits of Pi appear in a random order? If so, the trillions of digits of Pi calculated can serve as a useful random number generator. This post was inspired by this entry on Matt Asher's blog. Generating pseudo-random numbers is a key piece o...
Example 7.42: Testing the proportionality assumption
In addition to the non-parametric tools discussed in recent entries, it's common to use proportional hazards regression, (section 4.3.1) also called Cox regression, in evaluating survival data.It's important in such models to test the proportionality a...
Example 7.36: Propensity score stratification
In examples 7.34 and 7.35 we described methods using propensity scores to account for possible confounding factors in an observational study.In addition to adjusting for the propensity score in a multiple regression and matching on the propensity score...
Zero Inflated Models and Generalized Linear Mixed Models with R.
Zuur, Saveliev, Ieno (2012).
