"Isotonic regression is generally used to convert and approximate a data that is supposed to be only increasing" 

Applying isotonic regression is quite straight forward in R. The isoreg function comes handy for this, as it can be used on numeric data without supplying special arguments.
ir3 <- isoreg(y3 <- c(1, 0, 4, 3, 3, 5, 4, 2, 3)))
ir3$y # actuals
# [1] 1 0 4 3 3 5 4 2 3
ir3$yf # isotonic approximation
# [1] 0.50 0.50 3.33 3.33 3.33 3.50 3.50 3.50 3.50
plot(ir3) # graph
ir3$yf[ir3$iKnots] # Increasing points