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Convert all columns of a data frame to numeric in R To convert all the columns of the data frame to numeric in R, use the lapply() function to loop over the columns and convert to numeric by first converting it to character class as the columns were a factor.
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.
Convert character to numeric. To convert character values to numeric values, use the INPUT function. new_variable = input(original_variable, informat.); The informat tells SAS how to interpret the data in the original character variable.
To convert factors to the numeric value in R, use the as. numeric() function. If the input is a vector, then use the factor() method to convert it into the factor and then use the as. numeric() method to convert the factor into numeric values.
If we need only one column to be numeric
yyz$b <- as.numeric(as.character(yyz$b))
But, if all the columns needs to changed to numeric, use lapply to loop over the columns and convert to numeric by first converting it to character class as the columns were factor.
yyz[] <- lapply(yyz, function(x) as.numeric(as.character(x)))
Both the columns in the OP's post are factor because of the string "n/a". This could be easily avoided while reading the file using na.strings = "n/a" in the read.table/read.csv or if we are using data.frame, we can have character columns with stringsAsFactors=FALSE (the default is stringsAsFactors=TRUE)
Regarding the usage of apply, it converts the dataset to matrix and matrix can hold only a single class. To check the class, we need
lapply(yyz, class)
Or
sapply(yyz, class)
Or check
str(yyz)
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