PROC SGPLOT datastep

[lone0708]

Hi All,

I am working on a plot like this: https://blogs.sas.com/content/graphicallyspeaking/2018/03/02/series-plot-varying-attributes/

I am currently struggling with the datastep where I need to define that the last point of the previous curve segment is replicated as the first point of the next segment.

I have two dates defining the change in color. When age (age_measure) passes age 1, then I want a change in the color and again when age passes age 2 a new change in color. 
So I need to get the determinant of the colorresponse variable appear twice: Meaning age 1 appears both as colorresponse variabel 1 and 2, and age 2 appearing both as colorresponse variable 2 and 3 to get the datapoints to connect in the plot. 

Do you have any ideas on how to define that in a datastep? 

Example data below:

patientid = patient id, a1 = age 1, a2 = age 2, visit date = examination date, measure = measurement at examination date, age_measure = age at measurement. 

The curve is measure as a function of age_measure, where the curve needs to change color when age 1 and age 2 are passed (interpolated values of age_measure.). Age 1 always comes before age 2, but some patients jump directly to age 2. Some patients might not have either age 1 or 2. 
I don't know if this this possible in proc sgplot as the curve needs to "break" several times, like in a spaghetti-plot. But maybe proc gplot works, I have just never used that before. 

data patients;
input patientid $ a1 a2;
datalines;
1 32 34
2 23 .
3 22 35
4 30 31
5 . 28
;

data visits;
input patientid $ visit_date :yymmdd8. measure age_measure;
format visit_date yymmdd10.;
datalines;
1  20180101  3.4   20
1  20180505  2.3   35
2  20170210  7.3   15
2  20170217  7.2   24
2  20170220  7.1   35
3  20170221  5.4   33
4  20180202  3.4   30
4  20180204  3.2   37
5  20180504  5.6   28
5  20180505  5.0   32
;
data have;
merge
  patients
  visits
;
by patientid;
run;

[ballardw]

Data example is important.

Instructions here: https://communities.sas.com/t5/SAS-Communities-Library/How-to-create-a-data-step-version-of-your-dat... will show how to turn an existing SAS data set into data step code that can be pasted into a forum code box using the </> icon or attached as text to show exactly what you have and that we can test code against.

And then tell use where the curve change needs to happen.

[lone0708]

Dear Ballardw,
I have now updated the question