Splines

library(ramp.func)

tv = c(-1:6)*365/4
yv = c(1/2, 1, 2, 1, 1/3, 1, 3, 1) 
sp0 <- makepar_F_spline(tv, yv)

ff <- make_function(sp0)

tt = seq(0,550)
plot(tt, ff(tt), type = "l")