Warning message In invalid factor level NA generated

Question

I don t understand why I got this warning message    gt  fixed  lt - data frame  Type    character 3    Amount    numeric 3    gt  fixed 1     lt - c  lunch   100  Warning message  In    lt - factor    tmp    iseq  value    lunch       invalid factor level  NA generated  gt  fixed   Type Amount 1  lt NA gt     100 2           0 3           0

User · Answer

The easiest way to fix this is to add a new factor to your column   Use the levels function to determine how many factors you have and then add a new factor           gt  levels data Fireplace Qu       1   Ex   Fa   Gd   Po   TA       gt  levels data Fireplace Qu    c  Ex    Fa    Gd    Po    TA    None        1   Ex     Fa     Gd     Po      TA    None

User · Answer

Here is a flexible approach  it can be used in all cases  in particular     to affect only one column  or  the dataframe has been obtained from applying previous operations  e g  not immediately opening a file  or creating a new data frame       First  un-factorize a string using the as character function  and  then  re-factorize with the as factor  or simply factor  function   fixed  lt - data frame  Type    character 3    Amount    numeric 3      Un-factorize  as numeric can be use for numeric values                  as vector  can be use for objects - not tested  fixed Type  lt - as character fixed Type  fixed 1     lt - c  lunch   100     Re-factorize with the as factor function or simple factor fixed Type  fixed Type  lt - as factor fixed Type

User · Answer

The warning message is because your  Type  variable was made a factor and  lunch  was not a defined level  Use the stringsAsFactors   FALSE flag when making your data frame to force  Type  to be a character    gt  fixed  lt - data frame  Type    character 3    Amount    numeric 3    gt  str fixed   data frame     3 obs  of  2 variables     Type    Factor w  1 level     NA 1 1    Amount  chr   100   0   0   gt    gt  fixed  lt - data frame  Type    character 3    Amount    numeric 3  stringsAsFactors FALSE   gt  fixed 1     lt - c  lunch   100   gt  str fixed   data frame     3 obs  of  2 variables     Type    chr   lunch           Amount  chr   100   0   0

User · Answer

I have got similar issue which data retrieved from  xlsx file  Unfortunately  I could not find the proper answer here  I handled it on my own  with dplyr as below which might help others    install packages  xlsx   library xlsx  extracted df  lt - read xlsx  test xlsx   sheetName  Sheet1   stringsAsFactors FALSE    Replace all NAs in a data frame with  G  character extracted df is na extracted df    lt -  G    However  I could not handle it with the readxl package which does not have similar parameter to the stringsAsFactors  For the reason  I have moved to the xlsx package

User · Answer

If you are reading directly from CSV file then do like this   myDataFrame  lt - read csv  path to file csv   header   TRUE  stringsAsFactors   FALSE

[r] Warning message: In `...` : invalid factor level, NA generated

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