[R] Simple Coding problem ?

Jonathan Baron baron at cattell.psych.upenn.edu
Sun Apr 21 18:07:01 CEST 2002

On 04/21/02 10:33, Calvin L. Williams, Ph.D. wrote:
>This may be a simple problem, but I don't have an intuition of
>how simple it could be. Suppose I have a sequence of numbers
>corresponding to a series of diagnoses on the same patient
>over a sequence of time. The diagnoses are coded 1,2,3,4,5, but
>could come in a sequence like 1,3,2,5,3,5,...etc. Is there a simple
>way to count the number of times a 1 diagnosis is followed by a 2, or
>a 3, ... A 2 by a 1, or 3,....etc. It's almost like a mover-stayer problem.
>I think.

Suppose you have these in a vector v1.  How about something like

w1 <- length(v1)

If each subject is a row in a matrix m1, then you could do this
something like (where w1 is now the number of columns)

apply(m1,1,function(x) table(x[-w1],x[2:w1]))

I haven't tested this, and I might have it slightly wrong, or not

I'm sure there are better ways, but I'm sure this general idea
will work.

Jonathan Baron, Professor of Psychology, University of Pennsylvania
Home page: http://www.sas.upenn.edu/~baron
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