### Name: combine
### Title: Methods for Function combine in Package `Biobase'
### Aliases: combine combine,data.frame,data.frame-method
### Keywords: manip

### ** Examples

  x <- data.frame(x=1:5,
          y=factor(letters[1:5], levels=letters[1:7]),
          row.names=letters[1:5])
  y <- data.frame(z=3:7,
          y=factor(letters[3:7], levels=letters[1:7]),
          row.names=letters[3:7])
  combine(x,y)

  # y is converted to 'factor' with different levels
  x <- data.frame(x=1:5,y=letters[1:5], row.names=letters[1:5])
  y <- data.frame(z=3:7,y=letters[3:7], row.names=letters[3:7])
  try(combine(x,y))