Compare two Columns using index position in R : [![The dataframe][1]][1]

I have a scenario where I have to compare two columns in a dataframe. The condition is that the Field1 column has a set of values. Field2 column has few values and the remaining are NA. There is another column called Field3. So, the work here is to compare the Field1 values with Field2. The conditions to compare are as follows.

 1. If Field1 has a corresponding row in Field2. Copy the row value of Field2.
    Ex. Location and Place. So, I have to copy Place.

 2. If Field1 does not have a corresponding Field2 value. Then compare Field1 
    with Field3. Copy the Field3 value to Field2.

Kindly suggest a way to go about this.`dft = data.frame(Field1 = c("Location","Time","Date","Problem"), Field2 = c("Place","Balance","NA","NA"),
          Field3 = c("NA","NA","Pay","NA"))`

  [1]: https://i.stack.imgur.com/nPTpt.png

