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help for ^cart^ Version: 6/9/2004
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^Classification And Regression Tree analysis^
^-------------------------------------------^
^cart^ varlist [^if^] [^in^] ^, t^ime^(^var^) f^ail^(^var^)^
[ ^s^trata^(^varlist^) a^djust^(^varlist^) na^me^(^string^)^
^p^val^(^real 0.05^) mins^ize^(^int 10^) minf^ail^(^int 10^)^
^su^mby^(^varlist^) tab^by^(^varlist^)^ ^at(^string^)^]
^Description^
^-----------^
This program performs a CART analysis for failure time data. It uses
the martingale residuals of a Cox model to calculate (approximate)
chisquare values for all possible cutpoints on all the CART covariates.
^Varlist^
^-------^
The varlist (required with minimum one variable) specifies the independent
variables for CART. Observations with missing values on any of the variables
in this list are deleted.
^Options^
^-------^
^time()^ specifies the time variable. Observations with values <0 or missing
are deleted. Value 0 is replaced by a small positive value.
^fail()^ specifies the failure indicator. Observations with values <0 or missing
are deleted and values >0 are considered failures.
^strata()^ Optional. Specifies a varlist for a priori stratification of Cox model
^adjust()^ Optional. Specifies a varlist for apriori adjustment of Cox model.
Default the null Cox model will be used for calculation of the individual
relative hazard rate = exp(b'x), i.e. =1 in case of the null model,
which will form the basis for the calculation of the expected amount of
events for each subject within a CART subgroup.
However it is also possible to calculate the expected number after adjustment
for some variables and stratification by others.
This gives the opportunity to perform a CART for some variables after
adjustment and/or stratification by other variables in a Cox model.
The Cox model for adjustment and the associated exp(b'x) is fitted only once,
but the expected number of failures per subject is recalculated within each
CART subgroup.
^pval()^ specifies the maximum P-value for a split; default ^pval^=0.05.
P-values will be adjusted for the search of the optimal cutpoint within
a range within a group by the formulas of Miller&Siegmund and Worsley.
A split is not allowed if the adjusted minimum P-value is larger than ^pval^.
See Lausen for more details.
^minsize()^ specifies the minimum size of a subgroup for a split; default 10.
^minfail()^ specifies the minimum number of failures in a subgroup that is
required before a split will be attempted. Default 10.
^Output control:^
^sumby()^ specifies varlist for a summary of these variables by the final CART
grouping variable.
^tabby()^ specifies varlist for a tabulation of these variables by the final CART
grouping variable.
^at()^ specifies timepoints for display of survival probabilities by the final
CART grouping variable. See ^help sby^ for the use of the ^at^ option.
^name()^ specifies a name (default _cart) that will be used for
- the log-file
- the cart-tree graph
- the dta file with results
- the CART grouping variable.
The _cart splitting history is posted to a file with name x, default _cartx.
^References^
^----------^
Lausen et al, in Computational Statistics (Eds. P Dirschedl, R Ostermann),p 483-496, 1994.
Lausen et al, Informatik, Biometrie und Epidemiologie in Medizin und Biologie 28, 1-13, 1997
Miller and Siegmund, Biometrics 38, 1011-1016, 1982.
Worsley, Technometrics 25, 35-42, 1983.
^Author:^
^-------^
Wim van Putten
Erasmus MC - Daniel den Hoed Cancer Center
Rotterdam
The Netherlands
FAX: +31.10.4391028
e-mail: w.vanputten@@erasmusmc.nl