Introducing new populations in mathematica graphs

• Mathematica
hi i was wondering if anyone knew how to introduce different populations at diffrent times on the same plot on mathematica?
Say i wanted population 1 have n = 10 at t=0, population 2 to have n=4 at t=0 and then introduce a new population at t=25 so that population 3 would have n= 0 initally but then n= 1 at t = 25.
Any ideas? the only way I've been gettting around it is to give population 3 really small values initially (e.g. 0.000000000001) but its not very precise.

Dale
Mentor
2021 Award
What kind of plot are you using? If you are using list plot then you can specify both x and y coordinates in your list. e.g.

a = Transpose[{Range[10], 2 Range[10]}];
b = Table[{x, 13}, {x, 3, 10}];
ListPlot[{a, b}]

I'm using Plot [ndsolve] of a set of differential equations. Listplot won't seem to make a list of solutions. I want one populations to have initial conditions of 0 but then at a further time stage to have a vlaue of 1 and see how that changes.

Dale
Mentor
2021 Award
If popa and popb are the InterpolatingFunction objects that return from NDSolve then you can do the following:

truncate[f_InterpolatingFunction, t_] := If[f[[1, 1, 1]] <= t <= f[[1, 1, 2]], f[t]];
Plot[{truncate[popa, t], truncate[popb, t]}, {t, -1, 6}]