Find nearest points of latitude and longitude from different data sets with different length

Question

I have two data set of different stations. The data are basically data.frames with coordinates, longitudes and latitudes. Given the first data set (or vice versa), I want to

Answer 1

I don't exactly know what you want, but maybe this gives you some hints
if you want to get the min value for each column

  dd <- as.data.frame(dd)
  sapply(dd, min)
  paste(rownames(dd), ":", apply(dd,2,which.min)) #or