# Fill NA using last observation carried forward
locf <- na.locf(treasury_10)

# Fill NA using linear interpolation
approx <- na.approx(treasury_10)

# Fill NA using spline interpolation
spline <- na.spline(treasury_10)

# Merge into one object
na_filled <- merge(locf, approx, spline)

# Plot combined object
plot(na_filled, col = c("black", "red", "green"), 
     main = "Compare Interpolation Methods")