Macro 4 clean (Binomial tree option model)
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' Example: 1) enter f10 in B1
'          2) enter 7   in B2 
'          3) click the Macro add_row_column
'          4) copy 40 to all cells
'          5) run this macro 

Sub clean()
    Dim a As String
    Dim i, b, n As Integer
    Dim Range1 As Range
    a = Range("B1").Value
    n = Range("B2").Value
    For j = 1 To n - 1  ' clean up/down triangle
        For i = 1 To n - j
           Range(a).Offset(-i - j, j).Value =""
           Range(a).Offset(i + j, j).Value =""
        Next i
        Range(a).Offset(0, j).Value ="" 'clean row 0
    Next j
    For i = 1 To n 'clean the last column and S0 column
            Range(a).Offset(-n + 2 * i - 1, n).Value =""
            Range(a).Offset(i, 0).Value =""
            Range(a).Offset(-i, 0).Value =""
    Next i
    For j = 1 To n ' clean between last column
        For i = 1 To n
           b = -j + 2 * i - 1
           If b <= j Then
                Range(a).Offset(b, j).Value ="
           End If
         Next i
    Next j
End Sub

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Watch 2 vides on R installation
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Video to install R

How to download and install R (6m39s) [for windows)
    https://www.youtube.com/watch?v=ZoPJGmpYJzw

Programming in R - Getting Started - Installing R and RStudio on a Mac (5m59s)
    https://www.youtube.com/watch?v=Ywj6yNfc5nM

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find out all the 4-letter functions
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> .nLetterFunctions
function(n){
"Objective: show n-letter long functions

  Example #1: >.nLetterFunctions(3)

  Example #2: >.nlf(3)  # same as the above

  Example #3: >.nLetterFunctions(20)

";.nLetterFunctions_(n)}

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Estimate present values 
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  The present value of one future cash flow is given below
                  FV
     pv  =  --------------
               (1+R) ^n

   pv: present value 
   fv: future value
   R : effective period rate
   n : the number of periods

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