I want to add a column with name "category" to my data, how can i do that?
 input:
 col1 col2 col3 col4 col5 
 1     20   +    4     6 
 2     24   -    6     7
....

output:

 col1 col2 col3 col4 col5  col6
 1     20   +    4     6   category
 2     24   -    6     7   category
....

Assuming your data is in a data.frame called df:

• df$col6 <- "category" or
• df[["col6"]] <- "category" or
• data.frame(df, col6 = "category")
• ...