How to write a csv in F#?

Question

How would I write a record in F# into a csv? It would be optimal to have one row for each instance of a certain variable. My record and final output is a map like the one below.

type Family =
    { Month : int
      Year : int
      Income : float
      Family : int
      Dogs : int
      Cats : int
    }

let monthly =
    timeMap
    |> Seq.ofList
    |> Seq.map(fun ((month,year), rows) ->
        { Month = month
          Year = year
          Income = rows.Inc
          Family = familyMap.[(month,year)].Children
          Dogs = familyMap.[(month,year)].Dogs
          Cats = familyMap.[(month,year)].Cats
        })
    |> List.ofSeq

let map = 
    monthly
    |> List.map (fun x -> (x.Year,x.Month),x)
    |> Map.ofList

EDITED

This is what I have tried, but I am getting the error that (A,B,C,D,E,F) are not defined, and that it is recommended that I use the syntax new (type) args. This last error is showing up under >> MyCsvType

type MyCsvType = CsvProvider<Schema = "A (int), B (int), C (float), D (int), E (int), F (int)", HasHeaders = false>
let myCsvBuildRow (x:Family) = MyCsvType.Row(x.A,x.B,x.C,x.D,x.E,x.F)
let myCsvBuildTable = (Seq.map myCsvBuildRow) >> Seq.toList >> MyCsvType
let myCsv = monthly|> myCsvBuildTable
myCsv.SaveToString()

You may find that other question useful: https://stackoverflow.com/questions/33075932/how-to-create-a-csv-file-and-write-data-into-in-f — , Jun 30 '18 at 05:50
The accepted answer to the question I linked to perfectly answers your question on how to write a F# record to a CSV file, try to run the code and to adapt it to your situation. If there are parts that you don't understand, ask for an explanation but if you don't have time to try understanding the answer to your question, I'm afraid there's nothing I can do about that. — , Jun 30 '18 at 17:05
fair point. I have edited the code with issues I have. @ThomasCorbière — SantiClaus, Jun 30 '18 at 17:44
great, can we continue in some chat - it will be quicker? (SO or F# slack) — FoggyFinder, Jun 30 '18 at 19:13

score 4 · Accepted Answer · answered Jul 01 '18 at 21:57

Your code is almost there, except that the myCsvBuildRow function needs to access members of the Family type using their correct names. In your version, you are accessing names such as A, B, etc., but those are the names of columns in your CSV file, not the names of members of the F# record. The following does the trick for me:

type MyCsvType = CsvProvider<Schema = "A (int), B (int), C (float), D (int), E (int), F (int)", HasHeaders = false>

let myCsvBuildRow (x:Family) = 
  MyCsvType.Row(x.Month,x.Year,x.Income,x.Family,x.Dogs,x.Cats)
let myCsvBuildTable data = 
  new MyCsvType(Seq.map myCsvBuildRow data)

let myCsv = family |> myCsvBuildTable
myCsv.SaveToString()

How to write a csv in F#?

1 Answers1