[R] Re: how to add a column with string values to a data frame while still converting them to factors

[Uwe Ligges]

avneet singh wrote:

> i got the first part:
> 
> agm.data$ProdCategory=as.factor(agm.data$ProdCategory)
> 
> the second i am still struggling with


For the second part, see ?is.na.

Uwe Ligges


> 
> On 4/26/05, avneet singh <avneet.chugh at gmail.com> wrote:
> 
>>I have 2 questions. In essence i am trying to create product
>>categories based on product description and have it as an additional
>>column of my dataframe. some products dont fit any category and i need
>>a list of them. i am having some trouble in this simple (for most)
>>task.
>>Could you please provide suggestions. Thank you.
>>
>>avneet
>>
>>Question 1)
>>
>>I have a data frame
>>
>>
>>>agm.data=read.xls("agm.xls")
>>
>>i add a column to it by this and similar statements
>>
>>>agm.data$ProdCategory[agm.data$Product.Description=="PGX"|agm.data$Product.Description=="PGW"|agm.data$Product.Description=="PS"|agm.data$Product.Description=="PSX"]="Molded
>>
>>Graphite"
>>
>>if i do
>>
>>>agm.data$ProdCategory
>>
>>i get:
>>
>>  [1] "Extruded Graphite"   "Molded Graphite"     "Molded Graphite"
>>   [4] "Extruded Graphite"   "Extruded Graphite"   NA
>>   [7] "Molded Graphite"     "Extruded Graphite"   "Extruded Graphite"
>>  [10] "Extruded Graphite"   "Extruded Graphite"   "Extruded Graphite"
>>  [13] "Extruded Graphite"   "Porous"              "Iso-Molded Graphite"
>>.
>>.
>>.
>>.
>>.
>>[1222] "Extruded Graphite"   "Molded Graphite"     "Extruded Graphite"
>>[1225] "Extruded Graphite"   "Extruded Graphite"   NA
>>[1228] "Iso-Molded Graphite" "Extruded Graphite"   NA
>>
>>if i check the class, i get
>>
>>>is(agm.data$ProdC)
>>
>>[1] "character" "vector"
>>
>>i want this to have..
>>[1] "factor"   "oldClass"
>>
>>..like other columns have
>>
>>Question 2)some values of agm.data$ProdCategory are NA. i want to find
>>corresponding values of agm.data$Product.Description so i give the
>>following command
>>
>>>agm.data$Product.Description[agm.data$ProdCategory=="NA"]
>>
>>i get:
>>
>>[1] <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA>
>><NA> <NA> <NA>
>> [17] <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA>
>><NA> <NA> <NA>
>>.
>>.
>>.
>>.
>>.
>>.
>>[257] <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA>
>><NA> <NA> <NA>
>>[273] <NA> <NA> <NA> <NA> <NA>
>>165 Levels:  1.563x24 10x50x60 61x1.25 6x72 890S 8x6 9x7; 10x1.5 AGR ... YBDXX88
>>
>>--
>>God created man because he was disappointed over the apes. After that he has
>>given up any further experiments ~Mark Twain
>>
> 
> 
>