Extract time band data from a split Lexis object
The break points of a Lexis object (created by a call to
splitLexis) divide the follow-up intervals into time bands
along a given time scale. The breaks function returns
the break points, for a given time scale, and the timeBand
classifies each row (=follow-up interval) into one of the time bands.
timeBand(lex, time.scale, type="integer") breaks(lex, time.scale)
lex |
an object of class |
time.scale |
a character or integer vector of length 1 identifying the time scale of interest |
type |
a string that determines how the time bands are labelled. See Details below |
Time bands may be labelled in various ways according to the
type argument. The permitted values of the type
argument, and the corresponding return values are:
a numeric vector with integer codes starting from 0.
a factor (unordered) with labels "(left,right]"
the left-hand limit of the time band
the midpoint of the time band
the right-hand limit of the time band
The breaks function returns a vector of break points
for the Lexis object, or NULL if no break points have been
defined by a call to splitLexis. The timeBand
function returns a numeric vector or factor, depending on the value
of the type argument.
A newly created Lexis object has no break points defined.
In this case, breaks will return NULL, and
timeBand will a vector of zeros.
Martyn Plummer
data(diet)
diet <- cal.yr(diet)
diet.lex <- Lexis(entry=list(period=doe),
exit=list(period=dox, age=dox-dob),
exit.status=chd,
data=diet)
diet.split <- splitLexis(diet.lex, breaks=seq(40,70,5), "age" )
age.left <- timeBand(diet.split, "age", "left")
table(age.left)
age.fact <- timeBand(diet.split, "age", "factor")
table(age.fact)
age.mid <- timeBand(diet.split, "age", "mid")
table(age.mid)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.