F# deedle cast column datatype

Question

I have load a csv file to a Frame, deedle automatically infers that one column as decimal, whichi in fact should be int.

I have use the following line to do the casting into the correct type,

df?ColumnName <- df.GetColumn<int>("ColumnName")

I am wondering if this is the right way.

Answer 1

You can control the type of columns when reading .csv.

ReadCsv(...) has such parameter as schema:

schema - A string that specifies CSV schema. See the documentation for information about the schema format.

More information can be found here (in the section Controlling the column types)

Example:

.csv:

Name,Age,Comp1,Comp2
"Joe", 51, 12.1, 20.3
"Tomas", 28, 1.1, 29.3
"Eve", 2, 2.1, 40.3
"Suzanne", 15, 12.4, 26.3

F#:

let pathToCSV = "0.csv"
let schema = "Name,Age(int),Comp1,Comp2"

let loadFrame = Frame.ReadCsv(pathToCSV, schema=schema)
loadFrame.Format() |> printfn "%s"

loadFrame.ColumnTypes |> Seq.iter(printfn "%A")

Print:

     Name    Age Comp1 Comp2
0 -> Joe     51  12,1  20,3
1 -> Tomas   28  1,1   29,3
2 -> Eve     2   2,1   40,3
3 -> Suzanne 15  12,4  26,3

System.String
System.Int32
System.Decimal
System.Decimal

Although, for me, Frame have the correct column types and without specifying the schema.