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MathGroup Archive 2007

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Re: Mathematica code for survival functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg78316] Re: [mg78212] Mathematica code for survival functions
  • From: Darren Glosemeyer <darreng at wolfram.com>
  • Date: Thu, 28 Jun 2007 04:24:38 -0400 (EDT)
  • References: <200706260809.EAA03911@smc.vnet.net>

Coleman, Mark wrote:
> Greetings,
>
> Is anyone on MathGroup aware of Mathematica code that generates either
> Kaplan-Meier survival curves or life-table survival curves? Thanks.
>
> Best regards,
> Mark
>
>   

Here is a function that will give the Kaplan Meier fit as a Piecewise 
function. The first three arguments are lists of equal length for the 
times, survivor counts, and death counts. Your data may require some 
processing to get it into that form.

In[1]:= KMFit[times_, survivors_, deaths_, var_] := Piecewise[
          MapThread[{#1, #2 <= var < #3} &,
           {Join[{1}, With[{list = (survivors - deaths)/survivors},
              FoldList[Times, First[list], Drop[list, 1]]]], Join[{0}, 
times],
             Join[times, {Infinity}]}]]

Here is an example based on data from Table 1.4 in The Statistical 
Analysis of Failure Time Data by Kalbfleisch and Prentice.

In[2]:= t = {143, 164, 188, 190, 192, 206, 209, 213, 216, 220, 227, 230, 
234,
           246, 265, 304};

In[3]:= s = {19, 18, 17, 15, 14, 13, 12, 11, 10, 8, 7, 6, 5, 3, 2, 1};

In[4]:= d = {1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};

In[5]:= KMFit[t, s, d, x]

                                       18                    17
Out[5]= Piecewise[{{1, 0 <= x < 143}, {--, 143 <= x < 164}, {--, 164 <= 
x < 188},
                                       19                    19
 
       15                    14                    13
 >     {--, 188 <= x < 190}, {--, 190 <= x < 192}, {--, 192 <= x < 206},
       19                    19                    19
 
       12                    11                    10
 >     {--, 206 <= x < 209}, {--, 209 <= x < 213}, {--, 213 <= x < 216},
       19                    19                    19
 
       9                     63                     27
 >     {--, 216 <= x < 220}, {---, 220 <= x < 227}, {--, 227 <= x < 230},
       19                    152                    76
 
       45                     9                     3
 >     {---, 230 <= x < 234}, {--, 234 <= x < 246}, {--, 246 <= x < 265},
       152                    38                    19
 
       3
 >     {--, 265 <= x < 304}}]
       38


Darren Glosemeyer
Wolfram Research


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