      a     b c    
  <dbl> <int> <lgl>
1   1       1 TRUE 
2   2.5     2 FALSE
3  NA      NA NA   
  d     e    
  <chr> <fct>
1 a     a    
2 b     b    
3 <NA>  <NA> 
  f         
  <date>    
1 2015-12-10
2 2015-12-11
3 NA        
