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---- [求助]标准差的计算 (http://foxtable.com/bbs/dispbbs.asp?boardid=2&id=50013)
-- 发布时间：2014/4/27 22:28:00
--
可以参考这里
http://www.foxtable.com/help/topics/0545.htm
-- 发布时间：2014/4/27 22:29:00
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特殊计算，看这里，希望没有记错 标准差公式
For Each r As Row In Tables("表A").Rows
Dim datas(9) As Integer
For i As Integer = 0 To datas.length - 1
datas(i) = 2 ^ (r("log" & i))
Next
\'求平均值
Dim x As Double
For i As Integer = 0 To datas.length - 1
x = x + datas(i) / datas.length
Next
\'求平方差
Dim s2 As Double
For i As Integer = 0 To datas.length - 1
s2 = s2 + (datas(i) - x) ^ 2
Next
s2 = s2 / datas.length
Dim s As Double = math.Sqrt(s2)
r("标准差") = s
Next
-- 发布时间：2014/4/27 22:32:00
--
是这样？
For Each r As Row In Tables("表A").Rows
Dim datas(9) As Integer
For i As Integer = 0 To datas.length - 1
datas(i) = 2 ^ (r("log" & i))
Next
\'求平均值
Dim x As Double
For i As Integer = 0 To datas.length - 1
x = x + datas(i)
Next
x = x / datas.length
\'求平方差
Dim s2 As Double
For i As Integer = 0 To datas.length - 1
s2 = s2 + (datas(i) - x) ^ 2
Next
s2 = s2 / datas.length
Dim s As Double = math.Sqrt(s2)
r("标准差") = s
Next
-- 发布时间：2014/4/28 9:31:00
--
版主的公式还在理解当中，用实际数据检验，发现结果不对。比例在log8和log9这两列中，log8有3个，表示有3个2的8次方，即256,256,256这三个数;log9列有1个，表示有1个2的9次方数，即512。这四个数的标准差为128，套用版主的公式，结果为6.8922。不知我举例说得够不够明晰，请再看看。
哦，理解错了，那就改一下这里。
For Each r As Row In Tables("表A").Rows
Dim length As Integer
For i As Integer = 0 To 9
length += r("log" & i)
Next
Dim datas(length-1) As Integer
Dim idx As Integer = 0
For i As Integer = 0 To 9
For j As Integer = 1 To r("log" & i)
datas(idx) = 2 ^ i
idx += 1
Next
Next
\'求平均值
Dim x As Double
For i As Integer = 0 To datas.length - 1
x = x + datas(i)
Next
x = x / length
\'求平方差
Dim s2 As Double = 0
For i As Integer = 0 To datas.length - 1
s2 = s2 + (datas(i) - x) ^ 2
Next
s2 = s2 / length
Dim s As Double = math.Sqrt(s2)
r("标准差") = s
Next
-- 发布时间：2014/4/28 9:59:00
--
回复楼主，重新弄了一下。看6楼。发觉你给的数据不正确吧？
256,256,256,512的标准差，是128？怎么将计算的？难道我的公式记错了，伤不起啊
不要欺负我小学毕业
-- 发布时间：2014/4/28 11:07:00
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标准差应该是 =STDEVP(256,256,256,512) 吧？
-- 发布时间：2014/4/28 14:30:00
--
回复10楼，那就这样做
For Each r As Row In Tables("表A").Rows
Dim length As Integer
For i As Integer = 0 To 9
length += r("log" & i)
Next
Dim datas(length-1) As Integer
Dim idx As Integer = 0
For i As Integer = 0 To 9
For j As Integer = 1 To r("log" & i)
datas(idx) = 2 ^ i
idx += 1
Next
Next
\'求平均值
Dim x As Double
For i As Integer = 0 To datas.length - 1
x = x + datas(i)
Next
x = x / datas.length
\'求平方差
Dim s2 As Double = 0
For i As Integer = 0 To datas.length - 1
s2 = s2 + (datas(i) - x) ^ 2
Next
s2 = s2 / (datas.length -1)
Dim s As Double = math.Sqrt(s2)
r("标准差") = s
Next
-- 发布时间：2014/4/28 22:33:00
--
没有问题吧？你改一下你窗口的代码
If e.DataCol.Name="刷新" Then
If e.DataRow("刷新")=True Then
Dim r As DataRow = e.DataRow
Dim length As Integer
For i As Integer = 0 To 9
length += r("log" & i)
Next
Dim datas(length-1) As Integer
Dim idx As Integer = 0
For i As Integer = 0 To 9
For j As Integer = 1 To r("log" & i)
datas(idx) = 2 ^ i
idx += 1
Next
Next
\'求平均值
Dim x As Double
For i As Integer = 0 To datas.length - 1
x = x + datas(i)
Next
x = x / datas.length
\'求平方差
Dim s2 As Double = 0
For i As Integer = 0 To datas.length - 1
s2 = s2 + (datas(i) - x) ^ 2
Next
s2 = s2 / (datas.length -1)
Dim s As Double = math.Sqrt(s2)
r("标准差") = s
End If
End If