CODEWITHSUNDEEP
rinterpolation
pepece
pepece

Reputation: 370

Function na.approx refuses character

I would just like to interpolate by using the "constant" method but character seems not to be supported by approx function what could I do.

  library(zoo)     
  na.approx(c('a', NA, NA,'b', NA, NA,'a', NA, NA, NA, NA), 
            maxgap = 3,
            method = "constant")
  # should return : c('a', 'a', 'a','b', 'b', 'b','a', NA, NA, NA, NA)

Instead it gives the error message:

Error in approx(x[!na], y[!na], xout, ...) : zero non-NA points

Upvotes: 2

Views: 212

Answers (1)

mt1022
mt1022

Reputation: 17289

Edit

You should use na.locf:

na.locf(x, maxgap = 3, na.rm = FALSE)
 [1] "a" "a" "a" "b" "b" "b" "a" NA  NA  NA  NA

Original answer

na.approx only accept numeric vectors. But you can do this manually:

na.approx.char.con <- function(x, maxgap){
    ave(x, cumsum(!is.na(x)), FUN = function(x){
        if(length(x) > maxgap + 1){
            x
        }else{
            rep(x[1], length(x))
        }
    })
}

x <- c('a', NA, NA,'b', NA, NA,'a', NA, NA, NA, NA)
na.approx.char.con(x, maxgap = 3)
# [1] "a" "a" "a" "b" "b" "b" "a" NA  NA  NA  NA

Upvotes: 3

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