Introduction to Stata 8 - (GRIPS

. summarize
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
lbnr | 48 24.5 14 1 48
.... |
risktime | 48 1.291667 .8546908 .0833333 3.25
died | 48 .6458333 .4833211 0 1
_st | 48 1 0 1 1
_d | 48 .6458333 .4833211 0 1
_t | 48 1.291667 .8546908 .0833333 3.25
_t0 | 48 0 0 0 0
. save c:\dokumenter\proj1\st.cancer1.dta
Four new variables were created, and the st'ed data set is prepared for a number of incidence
rate and survival analyses:
_st 1 if the observation includes valid survival time information, otherwise 0
_d 1 if the event occurred, otherwise 0 (censoring)
_t time or age at observation end (here: risktime)
_t0 time or age at observation start (here: 0)
Summary of time at risk and incidence rates
stptime , by(drug) per(1000) dd(4)
stptime , at(0(1)5) by(drug)
[ST] stptime
// rates x 1000, 4 decimals
// 1-year intervals
A table of the survivor function:
sts list , by(drug) compare at(0(0.5)5)
[ST] sts list
// ½ year intervals
The corresponding graph:
[ST] sts graph
sts graph , by(drug)
To obtain a cumulative incidence (1–S) graph displaying the interval 0-0.25 at the y-axis:
sts graph , by(drug) failure ylabel(0(0.05)0.25)
A logrank test comparing two or more groups:
sts test drug
[ST] sts test
Cox proportional hazards regression analysis:
stcox drug01
xi: stcox i.drug
// drug dichotomized
// 3 drugs
[ST] stcox
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