r - How to associate variable values from a df to another -

i have dataframe 3 values, x , y coordinates , z value of indipendent variable:

x.range <- c(1,10) y.range <- c(20,50) grid <- expand.grid(x = seq(x.range[1], x.range[2], by=0.5),                         y = seq(y.range[1], y.range[2], by=0.5)) grid$z <- runif(nrow(grid),10, 70) 

now have dataframe x , y values:

x1 <- c(3.7,5.4,9.2) y1 <- c(41.1,30.3,22.9) df <- data.frame(x=x1,y=y1) 

now want associate points of dataframe df z value of nearest point of dataframe grid (with shortest distance). thanks.

this isn't prettiest, works

apply(df, 1,        function(x){         pythag <- sqrt((x[1] - grid$x)^2 +                         (x[2] - grid$y)^2)         grid[which.min(pythag), "z"]       }) 

simply returning value nearest point using pythagoras.

edit

recoding adhere coding standards:

pythag <- function(x, y, g){   which.min(((x - g$x)^2 + (y - g$y)^2)^0.5) }  idx <- mapply(fun = pythag,               x = df[["x"]],                y = df[["y"]],                moreargs = list(g = grid))  grid[idx,]