R help - Nov 2015 - Returning a factor from vapply

Hello, 

I would like to return a factor from vapply, which looks it cannot be done
directly since a factor is typeof() numeric. So I?m not sure if the solution
below is the standard approach to handle this. My concern is that the factor
levels are mixed up in the results (as shown in the last line of code), which is
undesirable.

set.seed(1)
df <- data.frame(x1 = runif(100), x2 = runif(100))


mycuts <- function(x) {
  
  xc <- cut(x, breaks = unique(quantile(x, seq(0, 1, 1/4), na.rm = TRUE)),
            include.lowest = TRUE)
  as.character(xc)
  
}

head(df_out <- data.frame(vapply(df, mycuts, character(nrow(df)))))

identical(levels(df_out$x1), levels(cut(df$x1, breaks = unique(quantile(df$x1, 
                                        seq(0, 1, 1/4), na.rm = TRUE)),
                                        include.lowest = TRUE)))


Thanks for any pointers. 

Axel.

Such manipulations are usually better performed in character data.  Convert to
factor only after the vector is complete.
-- 
Sent from my phone. Please excuse my brevity.

On November 25, 2015 3:49:24 AM PST, Axel Urbiz <axel.urbiz at gmail.com>
wrote:
>Hello, 
>
>I would like to return a factor from vapply, which looks it cannot be
>done directly since a factor is typeof() numeric. So I?m not sure if
>the solution below is the standard approach to handle this. My concern
>is that the factor levels are mixed up in the results (as shown in the
>last line of code), which is undesirable. 
>
>set.seed(1)
>df <- data.frame(x1 = runif(100), x2 = runif(100))
>
>
>mycuts <- function(x) {
>  
>xc <- cut(x, breaks = unique(quantile(x, seq(0, 1, 1/4), na.rm
>TRUE)),
>            include.lowest = TRUE)
>  as.character(xc)
>  
>}
>
>head(df_out <- data.frame(vapply(df, mycuts, character(nrow(df)))))
>
>identical(levels(df_out$x1), levels(cut(df$x1, breaks
>unique(quantile(df$x1,
>                                        seq(0, 1, 1/4), na.rm = TRUE)),
>                                        include.lowest = TRUE)))
>
>
>Thanks for any pointers. 
>
>Axel.
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