[<Literal>]
let sample = "C:/FSharp/sample.csv"
let r = Frame.ReadCsv(sample,missingValues=[|""|]).IndexRows<int>("row")
r.Rows.[2].As<float>()

val r : Frame<int,string> =
  
     c1        c2 c3        
1 -> <missing> 5  <missing> 
2 -> 4         6  <missing> 

val it : Series<string,float> =
  
c1 -> 4         
c2 -> 6         
c3 -> <missing> 

val r : Frame<int,string> =
     c1        c2 c3 
1 -> <missing> 5  	  
2 -> 4         6     

System.FormatException: Input string was not in a correct format.