I happened to come across a user written program which might be the solution to what I am attempting to do (compare a published KM curve to one we are working on locally).

I am using ipdfc which was written to reconstruct individual participant data from a published Kaplan-Meier curve (findit ipdfc).

I have digitised the KM curve from the following paper and wanted to use the ipdfc command to reconstruct the individual participant data.

https://www.ncbi.nlm.nih.gov/pmc/art...v038p00769.pdf

based on this, i have extracted the following data and points.

Code:
femalesagexdermott femalesproportionydermott
2.250259 1.0009734
6.7189907 .99996194
11.187561 1.000384
15.656271 .99956804
20.125786 .99158437
24.48281 .98801388
29.064506 .97837551
33.345984 .97288928
38.048789 .93842834
42.476369 .92490446
47.000088 .9079631
51.273208 .87864681
54.617883 .81446671
58.031029 .73895572
62.397216 .70367233
65.917298 .62334907
67.837164 .58112485
68.801202 .52348231
70.192767 .44853756
72.75203 .3972092
75.418717 .33673176
77.021841 .27274933
79.189122 .21373451
81.609278 .16217862
83.74858 .06082447
You may note that the source publication does not include a risk table, so i am clean out of luck there. However, i have read from the help file associated with ipdfc, an approach is to enter 0 for the trisk option and the total number of participants (60) for the nrisk option.

Armed with all this, i have put together the following syntax

Code:
ipdfc, surv(femalesproportionydermott) tstart(femalesagexdermott) trisk(0) nrisk(60) generate(FEMALEDERMOTT1 FEMALEDERMOTT2) saving(TEST2) proportion isotonic
This returns:

Code:
0 invalid name
(error in option trisk())
if i stipulate a dummy variable for both
Code:
gen DUMMYZERO=0
gen POPULATION=60
Re-running the command:

Code:
ipdfc, surv(femalesproportionydermott) tstart(femalesagexdermott) trisk(DUMMYZERO) nrisk(POPULATION) generate(FEMALEDERMOTT1 FEMALEDERMOTT2) saving(TEST2) proportion isotonic
this returns:

Code:
'0' invalid observation number
It is of note that the command is at least doubling the number of lines in the file at some stage in its execution, but provides the error.


I am using Stata 15.1 IC. I have also attempted to specify previous versions 14 and 13 using the version command to get this working. A colleague has tried on Stata 16 also, but to no avail.

I have also tried to contact the original authors of the program, but their Stata profiles did not come up when i looked them up by name.

A Google search and a search on the Stata forum has provided little further insight.

Does anyone out there have experience using this ado in situations where the life table is not available?

Thanks in advance,

Geoff