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I have a data frame with all factor values
V1 V2 V3
a b c
c b a
c b c
b b a
How can I convert all the values in the data frame to a new one with numeric values (a to 1, b to 2, c to 3, etc ...)
562
There are two steps for converting factor to numeric: Step 1: Convert the data vector into a factor. The factor() command is used to create and modify factors in R. Step 2: The factor is converted into a numeric vector using as. numeric().
To convert columns of an R data frame from integer to numeric we can use lapply function. For example, if we have a data frame df that contains all integer columns then we can use the code lapply(df,as. numeric) to convert all of the columns data type into numeric data type.
To convert a column to numeric in R, use the as. numeric() function. The as. numeric() is a built-in R function that returns a numeric value or converts any value to a numeric value.
I would try:
> mydf[] <- as.numeric(factor(as.matrix(mydf)))
> mydf
V1 V2 V3
1 1 2 3
2 3 2 1
3 3 2 3
4 2 2 1
Converting from factor to numericgives the integer values. But, if the factor columns have levels specified as c('b', 'a', 'c', 'd') or c('c', 'b', 'a'), the integer values will be in that order. Just to avoid that, we can specify the levels by calling the factor again (safer)
df1[] <- lapply(df1, function(x)
as.numeric(factor(x, levels=letters[1:3])))
If we are using data.table, one option would be to use set. It would be more efficient for large datasets. Converting to matrix may pose memory problems.
library(data.table)
setDT(df1)
for(j in seq_along(df1)){
set(df1, i=NULL, j=j,
value= as.numeric(factor(df1[[j]], levels= letters[1:3])))
}
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