psych (version 1.0-77)

comorbidity: Convert base rates of two diagnoses and their comorbidity into phi, Yule, and tetrachorics

Description

In medicine and clinical psychology, diagnoses tend to be categorical (someone is depressed or not, someone has an anxiety disorder or not). Cooccurrence of both of these symptoms is called comorbidity. Diagnostic categories vary in their degree of comorbidity with other diagnostic categories. From the point of view of correlation, comorbidity is just a name applied to one cell in a four fold table. It is thus possible to analyze comorbidity rates by considering the probability of the separate diagnoses and the probability of the joint diagnosis. This gives the two by two table needed for a phi, Yule, or tetrachoric correlation.

Usage

comorbidity(d1, d2, com, labels = NULL)

Arguments

d1

Proportion of diagnostic category 1

d2

Proportion of diganostic category 2

com

Proportion of comorbidity (diagnostic category 1 and 2)

labels

Names of categories 1 and 2

Value

• twobytwo
  The two by two table implied by the input
• phi
  Phi coefficient of the two by two table
• Yule
  Yule coefficient of the two by two table
• tetra
  Tetrachoric coefficient of the two by two table

See Also

phi, Yule

Examples

if(require(polycor)) {comorbidity(.2,.15,.1,c("Anxiety","Depression")) }