as.factor does not work inside function
Hi Xiaobo, The problem is that your function is not assigning the results to your data frame---df is an internatl copy made by the function. This is done to prevent calling functions to have unexpected events such as overwriting objects in the global environment. Anyway, I think you can accomplish what you want using lapply(): ## your data df <- data.frame(x=1:5, y=2:6) ## apply the function, as.factor() to all the elements in the first argument ## and save the results in the relevant columns of df df["x"] <- lapply(df["x"], as.factor) ## check results is.factor(df[, "x"]) Hope this helps, Josh
On Sat, Dec 10, 2011 at 6:06 PM, Xiaobo Gu <guxiaobo1982 at gmail.com> wrote:
Hi,
I am trying to write a function do cast columns of data frame as
factor in a loop, the source is :
as.factor.loop <- function(df, cols){
? ? ? ?if (!is.null(df) && !is.null(cols) && length(cols) > 0)
? ? ? ?{
? ? ? ? ? ? ? ?for(col in cols)
? ?{
? ? ? ? ? ? ? ? ? ? ? ?df[[col]] <- as.factor(df[[col]])
? ? ? ? ? ? ? ?}
? ? ? ?}
}
source('D:/ambertuil.r')
x <- 1:5
y <- 2:6
df <- data.frame(x=x, y=y)
as.factor.loop(df, c("x"))
But after the function call, the df data frame does not change,
because
is.factor(df[["x]])
FALSE
But if I call this in R console directlly, it works
for(col in c("x","y")){df[[col]] <- as.factor(df[[col]])}
is.factor(df[["x]])
FALSE
Regards,
Xiaobo Gu
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Joshua Wiley Ph.D. Student, Health Psychology Programmer Analyst II, Statistical Consulting Group University of California, Los Angeles https://joshuawiley.com/