How to interpolate growth data using cubic spline

[hh9]

Hi SAS experts!

I need help with interpolate growth data using cubic spline model. I have multiple measures for each participant  but at different timepoint, my question is how can I get their predicted weight at the exact 0, 6, 12, 24, 36 months using cubic spline model? Thanks in advance for your help.

My data is 

DATA Have;
INPUT id age weight;
DATALINES;
1 0 4
1 2.2 6
1 5 8
1 10 20
1 11.3 28
1 28 40
1 40 53
2 0 3
2 1.5 8
2 4.9 15
2 6.4 20
2 14.9 40
2 31 50
2 41 66
3 0 6
3 2.8 11
3 6.1 23
3 9.4 36
3 19.1 40
3 37 51
;
RUN;

[Oligolas]

Hi,

have a look at these blog entries:

https://blogs.sas.com/content/iml/2020/05/11/cubic-interpolation-sas.html 

https://github.com/sascommunities/the-do-loop-blog/blob/master/interpolation/cubicInterp.sas 

Unfortunately it does not work on my machine, so I can not try it.