How to convert an array of strings to an array float and replace Double.NaN for non-numeric values?

Question

I am writing a parser for CSV data and trying to determine how to process records that are empty (") or contain character data (" C "). The parser code that I have below works fine, but makes me deal with converting the float later I would like my string [] [] to be float [] [] and handle the conversions when parsing the file, but I notice that it explodes with any non-numeric data. Ideally there should be no numerical or empty values, but they inevitable and, as such, should be considered.

Can someone recommend a brief approach to trying to convert to Double, and then if it doesn't work, replace Double.NaN instead? (Without sacrificing great efficiency, if possible). Thank.

let stringLine = [| "2.0"; "", "C"|]
let stringLine2Float = Array.map float stringLine

//desiredFloatArray = [| 2.0; Double.NaN; Double.NaN |]


type csvData = { mutable RowNames: string[]; mutable ColNames: string[]; mutable Data: string[][] }

let csvParse (fileString: string) = 
    let colNames = ((fileLines fileString |> Seq.take 1 |> Seq.nth 0).Split(',')).[1..]
    let lines = fileLines fileString |> Seq.skip 1 |> Array.ofSeq
    let rowNames = Array.init lines.Length string;
    let allData : string [][] = Array.zeroCreate rowNames.Length 

    for i in 0..rowNames.Length - 1 do 
        let fields = lines.[i].Split(',') 
        allData.[i] <- fields.[1..]
        rowNames.[i] <- fields.[0]

    { RowNames = rowNames; ColNames = colNames; Data = allData }

Answer 1

Use this instead of the inline conversion float:

let cvt s =
  let (ok,f) = System.Double.TryParse(s)
  if ok then f else nan