st: Spline after Cox regression

[Etan Lakam <etan.lakam@googlemail.com>]

Dear Listers,
I am doing Cox-regression with a continuous exposure ffa and the
outcome hf, I have been trying to model it as  cubic spline.
Here is how I approached it, adjusting for age, sex, and race, however
it is coming up with the message error below, and I cannot obtain the
graph
I do not have a clue about what is happening.
Thank you in advance for your help.
Best,
Etan


mkspline  rlnffa= lffa, cubic nknots(5)
stcox rlnratio* sex race age
adjust race=0 sex=1 age, by(lnffa) ci replace exp
------------------------------------------------------------------------------------------
     Dependent variable: _t     Command: stcox
   Variables left as is: rlnffa1, rlnffa2
  Covariate set to mean: age = 53.900191
Covariates set to value: race = 0, sex = 1
------------------------------------------------------------------------------------------
too many values
r(134);
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/