VB 画lg坐标系，两个纵轴

[dou1746]

有大神 做过lg坐标系的吗？
纵坐标是lg
做出来的效果个excel的lg一样

[脆皮大雪糕]

无非就是数值经过Log计算以后再映射到Y坐标上咯

[脆皮大雪糕]

闲着，写个例子吧，新建工程，窗体拉大点，放一个picturebox,一个按钮，然后黏贴下面的代码

    Dim X0 As Long, Y0 As Long '坐标原点在picture中的坐标
    Dim lngBorder As Long  '图像相对于picture边框留空距离
    Dim XMAX As Double, YMAX As Double '坐标上 XY所能表示的最大值，这里默认最小值为0，懒得倒腾负数了，有需要自己改

Private Sub Command1_Click()
    
    Picture1.Width = 6000
    Picture1.Height = 6000
    Picture1.ScaleHeight = Picture1.Height
    Picture1.ScaleWidth = Picture1.Width

    Dim test(1 To 10) As Double
    Dim i As Integer
    For i = 1 To 10
        test(i) = Exp(i + (Rnd() - 0.5) * i * 0.3) 'f(i) = exp(i) 在ln坐标系下应该是一条直线，加一点随机干扰让线条不要太直
    Next
    Render test
End Sub

Private Sub Render(data() As Double)

    XMAX = 10: YMAX = 37000  'Y最大值根据用例，最大可能值是 exp(10.5) = 36315 我们取 37000
    
    lngBorder = 400
    X0 = lngBorder: Y0 = Picture1.ScaleHeight - lngBorder '坐标原点定义
    
    Picture1.Cls
    '画坐标系
    Picture1.DrawWidth = 1
    Dim i As Long, j As Long
    Picture1.Line (X0 - lngBorder / 2, Y0)-(Picture1.ScaleWidth - lngBorder / 2, Y0), vbBlue
    Picture1.Line (X0, Y0 + lngBorder / 2)-(X0, lngBorder / 2), vbBlue

    For j = 0 To 4
        For i = 10 ^ j To 10 ^ (j + 1) Step 10 ^ j
            Picture1.Line (X0, TRANY(i))-(Picture1.ScaleWidth - lngBorder / 2, TRANY(i)), RGB(200, 200, 255)
        Next
        Picture1.CurrentX = 0: Picture1.CurrentY = TRANY(i - 1) - 100: Picture1.Print Trim(Str(i - 10 ^ j))
    Next
    
    '画曲线
    Picture1.CurrentX = X0 + LBound(data) / XMAX * (Picture1.ScaleWidth - lngBorder * 2)
    Picture1.CurrentY = TRANY(data(LBound(data)))
    Picture1.DrawWidth = 2
    For i = LBound(data) To UBound(data)
        Picture1.Line -(X0 + i / XMAX * (Picture1.ScaleWidth - lngBorder * 2), TRANY(data(i))), RGB(255, 0, 0)
    Next
    '标注数值
    For i = LBound(data) To UBound(data)
        Picture1.CurrentX = X0 + i / XMAX * (Picture1.ScaleWidth - lngBorder * 2)
        Picture1.CurrentY = TRANY(data(i)) + 100
        Picture1.Print Round(data(i), 2)
    Next
End Sub
Private Function TRANY(ByVal dblIn As Double) As Double
    TRANY = Y0 - (Log(dblIn) / Log(YMAX)) * (Picture1.ScaleHeight - lngBorder * 2)
End Function

[赵4老师]

自绘是早晚要学会的技能。