R help - Aug 2015 - Question about survival::survfit

I am wanting to do a KM curve of two groups using survival. For some
reason, the summary(survfit) gives me the following output:



           records n.max n.start events median 0.95LCL 0.95UCL

VAR=N   10931 10931   10931   1646     NA      NA      NA

VAR=Y    3452  3452    3452    906     NA      NA      NA



I am not sure why it won?t give me median survival for each group?  There
are no NA in my data.



Thanks very much

	[[alternative HTML version deleted]]

> On Aug 5, 2015, at 9:25 AM, Evan Kransdorf <evan.kransdorf at
gmail.com> wrote:
> 
> I am wanting to do a KM curve of two groups using survival. For some
> reason, the summary(survfit) gives me the following output:
> 
> 
> 
>           records n.max n.start events median 0.95LCL 0.95UCL
> 
> VAR=N   10931 10931   10931   1646     NA      NA      NA
> 
> VAR=Y    3452  3452    3452    906     NA      NA      NA
> 
> 
> 
> I am not sure why it won?t give me median survival for each group?  There
> are no NA in my data.
> 
> 
> 
> Thanks very much

Presumably, because the survivorship function never crosses below 0.5. You may
need to refresh yourself on the definition of median survival.

Plot the curves to visually confirm.

Regards,

Marc Schwartz