Here are a couple of examples of making spaghetti plots.
Here is a basic spaghetti plot that looks at "alcuse" over time (age_14) showing one regression line per person (see "search spagplot")
spagplot alcuse age_14 , id( id )
Here we make the same graph manually.
use https://stats.idre.ucla.edu/stat/stata/examples/alda/data/alcohol1_pp, clear quietly xi: regress alcuse i.id*age_14 predict yhat graph twoway line yhat age_14, connect(L L) And here is the graph
But say that you wanted to see separate lines for males and females. We can do that, as shown below.
use https://stats.idre.ucla.edu/stat/stata/examples/alda/data/alcohol1_pp, clear separate alcuse, by(male) quietly xi: regress alcuse0 i.id*age_14 predict yhat0 quietly xi: regress alcuse1 i.id*age_14 predict yhat1 graph twoway line yhat0 yhat1 age_14, connect(L L)
and here is the graph
