Numeric variables converted to factors when reading a CSV file

csv, r, read.table

Solution

Your `NA` strings in the csv file, `N/A`, are interpreted as `character` and then the whole column is converted to `character`. If you have `stringsAsFactors = TRUE` in `options` or in `read.csv` (default), the column is further converted to `factor`. You can use the argument `na.strings` to tell `read.csv` which strings should be interpreted as `NA`.

A small example:

df <- read.csv(text = "x;y
                 N/A;2,2
                 3,3;4,4", dec = ",", sep = ";")
str(df)

df <- read.csv(text = "x;y
                 N/A;2,2
                 3,3;4,4", dec = ",", sep = ";", na.strings = "N/A")
str(df)

Update following comment

Although not apparent from the sample data provided, there is also a problem with instances of '$' concatenated to the numbers, e.g. '$3,3'. Such values will be interpreted as `character`, and then the `dec = ","` doesn't help us. We need to replace both the '$' and the ',' before the variable is converted to numeric.

df <- read.csv(text = "x;y;z
               N/A;1,1;2,2$
               $3,3;5,5;4,4", dec = ",", sep = ";", na.strings = "N/A")
df
str(df)

df[] <- lapply(df, function(x){
  x2 <- gsub(pattern = "$", replacement = "", x = x, fixed = TRUE)
  x3 <- gsub(pattern = ",", replacement = ".", x = x2, fixed = TRUE)
  as.numeric(x3)
  }
                         )
df
str(df)

Problem

I'm trying to read a .csv file into R where all the column are numeric. However, they get converted to factor everytime I import them. Here's a sample of how my CSV looks like: This is my code: ``` options(StringsAsFactors=F) data<-read.csv("in.csv", dec = ",", sep = ";") ``` As you can see, I set `dec` to `,` and `sep` to `;`. Still, all the vectors that should be numerics are factors! Can someone give me some advice? Thanks!

Original source