How to convert all column data type to numeric and character dynamically?

Question

I convert my columns data type manually:

data[,\'particles\'] <- as.numeric(as.character(data[,\'particles\']))

This not ideal as the da

Answer 1

If you don't know which columns need to be converted beforehand, you can extract that info from your dataframe as follows:

vec <- sapply(dat, is.factor)

which gives:

> vec
particles  humidity timestamp      date 
     TRUE      TRUE     FALSE     FALSE 

You can then use this vector to do the conversion on the subset with lapply:

# notation option one:
dat[, vec] <- lapply(dat[, vec], function(x) as.numeric(as.character(x)))
# notation option two:
dat[vec] <- lapply(dat[vec], function(x) as.numeric(as.character(x)))

If you want to detect both factor and character columns, you can use:

sapply(dat, function(x) is.factor(x)|is.character(x))

Answer 2

Use lapply:

cols <- c("particles", "nox", ...)

data[,cols] <- lapply(data[,cols], function(x) as.numeric(as.character(x)))

Answer 3

Another option using mutate_if() from dplyr which allows you to operate on columns for which a predicate returns TRUE

library(dplyr)
df %>% 
  mutate_if(is.factor, funs(as.numeric(as.character(.))))

Note: This method will work for your follow up question as well

Answer 4

We can use data.table

library(data.table) 
setDT(df)[, lapply(.SD, function(x) if(is.factor(x)) as.numeric(as.character(x)) else x)]

Answer 5

The best option is I think apply

You can do

newD<-apply(data[,"names"], 2,function(x) as.numeric(as.character(x)))

where in "names" you put all the variables you want. Then apply with 2 as second argument will apply the function(x) on all the columns(if you put 1 its by rows) of the first argument. And you can save it as new dataset or rewrite the old one with

data[,"names"]<-apply....