R：将一列中的因子值应用于另一列

Question

I am trying to process municipal information in R and it seems that factors (to be exact factor() ). are the best way to achieve my goal. I am only starting to get the hang of R, so I imagine my problem is possibly very simple.

I have the following example dataframe to share (a tiny portion of Finnish municipalities):

municipality<-c("Espoo", "Oulu", "Tampere", "Joensuu", "Seinäjoki", 
"Kerava")
region<-c("Uusimaa","Pohjois-Pohjanmaa","Pirkanmaa","Pohjois-Karjala","Etelä-Pohjanmaa","Uusimaa")

myData<-cbind(municipality,region)
myData<-as.data.frame(myData)

By default R converts my character columns into factors, which can be tested with str(myData) . Now to the part where my beginner to novice level R skills end: I can't seem to find a way to apply factors from column region to column municipality .

Let me demonstrate. Instead of having the original result

as.numeric(factor(myData$municipality))

[1] 1 4 6 2 5 3

I would like to get this, the factors from myData$region applied to myData$municipality.

as.numeric(factor(myData$municipality))

[1] 5 4 2 3 1 5

I welcome any help with open arms. Thank you.

Answer 1

To better understand the use of factor in R have a look here .

If you want to add factor levels, you have to do something like this in your dataframe:

levels(myData$region)
[1] "Etelä-Pohjanmaa"   "Pirkanmaa"         "Pohjois-Karjala"   "Pohjois-Pohjanmaa" "Uusimaa"          
> levels(myData$municipality)
[1] "Espoo"     "Joensuu"   "Kerava"    "Oulu"      "Seinäjoki" "Tampere"  
> levels(myData$municipality)<-c(levels(myData$municipality),levels(myData$region))
> levels(myData$municipality)
 [1] "Espoo"             "Joensuu"           "Kerava"            "Oulu"              "Seinäjoki"        
 [6] "Tampere"           "Etelä-Pohjanmaa"   "Pirkanmaa"         "Pohjois-Karjala"   "Pohjois-Pohjanmaa"
[11] "Uusimaa"