小编Haa*_*Daz的帖子

我怎样才能在f sharp中创建一个csv文件并在其中写入以下记录类型？

    type test = { G:array<double>; P:array<double>; GG:array<double>; PP:array<double> } 

    let table = [for x in 0..(Un0.Length - 1) -> 
        let b = Un0.[x] in 
        if b=0.0 then {G=0.0; P=0.0; GG=0.0; PP=0.0}
        else {G=G_0.[x]/b; P=P0.[x]/b; GG=G0.[x]/b; PP=PP0.[x]/b}]

如何同时并行运行这两个独立循环.

let a1=Seq.map2 (fun a b->(1.0-a)/(a-b)) a2  a3

let b1=Seq.map2 (fun a b->a*b) b2 b3

我有两个数据框df1和df2.我想创建一个新的数据帧df3是简单的总和df1,并df2在列名相同.

df1 <- data.frame(x1=c(1,4,5),x2=c(5,6,7),x3=c(9,9,10))
df2 <- data.frame(x1=c(1,6,3),x2=c(4,3,1),x3=c(5,4,6),x4=c(7,6,7))

 df1
    x1  x2  x3
 1  1   5   9
 2  4   6   9
 3  5   7   10

df2
    x1  x2  x3  x4
 1  1   4   5   7
 2  6   3   4   6
 3  3   1   6   7

df3
    x1  x2  x3  x4
 1  2   9   14  7
 2  10  9   13  6
 3  8   8   16  7

如何将obj列表转换为int类型.我试图使用下面的地图函数添加两个列表,但它不适用于obj列表.

let query f= 
 seq{
let cmd = new OleDbCommand( "SELECT *  FROM F" );
let conn = new OleDbConnection( @"Provider=Microsoft.ACE.OLEDB.12.0;
Data Source=D:\Users\df\Documents\Vfolio.accdb;
Persist Security Info=False;" )

conn.Open()
let DAdapt = new OleDbDataAdapter("SELECT * FROM F",conn)
let DTab = new DataSet()
let i= DAdapt.Fill(DTab)
let rowCol = DTab.Tables.[0].Rows
let rowCount = rowCol.Count
 for i in 0 .. (rowCount - 1) do
           yield f (rowCol.[i])
   }
 let u= query(fun row -> row.[0])
 let a= List.ofSeq u
 let v=query(fun row -> row.[1]) …

有三种相同尺寸的seq

a:int   = {1,  2,  3,  4}
b:string= {"a","b","a","d"}
c:string= {"y","y","t","t"}

如何从seq:a条件创建新的seq

where b="a" and c="y"