survexp.fit(x, y, times, conditional, ratetable)
x
| The first column contains the group, an integer value that divides the subjects into subsets. Remaining columns must match the dimensions of the ratetable, in the correct order. |
y
| the follow up time for each subject. |
times
| the vector of times at which a result will be computed. |
conditional
| if T compute the conditional survival, if false compute cohort survival. |
ratetable
| a rate table, such as survexp.uswhite. |
times
should be a superset of y
, so that each
subject at risk is at risk for the entire sub-interval of time.
For a large data set, however, this can use an inordinate amount of
storage and/or compute time. If the times
spacing is more coarse than
this, an actuarial approximation is used which should, however, be extremely
accurate as long as all of the returned values are > .99.
For a subgroup of size 1 and times
> y
,
the conditional method reduces to exp(-h) where
h is the expected cumulative hazard for the subject over his/her
observation time. This is used to compute individual expected survival.
survexp
.
Consequently, this function has very few error checks on its input arguments.
survexp
, survexp.us