R inverse CDF for a vector -

i have vector cumulative distribution function, let in form

y=seq(0, 1.0, 0.05) 

now need function inverse cdf of y,

f(0.1)=3    

and

f(0.9)=19 

any ideas how this?

the which function this.

> y <- seq(0, 1.0, 0.05) > which(y == .1) [1] 3 > which(y == .9) [1] 19 

however, if trying find inverse cdf, might have deal 2 vectors x , y, since possible x take indices values. might want this.

> y <- seq(0, 1.0, 0.05) > x <- 1:21 > x[which(y == .1)] [1] 3 > x[which(y == .9)] [1] 19