matrix function to do this?

[Puppet_Sock]

I have a column of data.

12.3
3.5
7.8
8.5
...etc.
9.4

It is 16 elements in length, but the number 16 may be different for
different cases.

These are the values of a diagonal 16x16 matrix.
12.3 0 0 0 etc.
0 3.5 0 0 etc.
0 0 7.8 0 etc.
etc.

What I want is a way to store the data as the column, but have it
behave like the diagonal matrix when I do things like mmult,
transpose, minverse, etc. It would be cool if there was something like
mdiag(a,b,c,d) that would create a matrix that was zero off diagonal,
and had the values a, b, c, d, down the diagonal.

Is there anything like that?
Socks

 

[Pete_UK]

You can create a matrix from that data quite easily. Suppose the data
is in column A, with the 12.3 value in A2. Put this formula in C2:

=IF(COLUMN(A1)=ROW(A1),$A2,0)

Then copy this across for however many rows you have in your original
list, and then copy that block of formulae down as required.

Hope this helps.

Pete

 

[Puppet_Sock]

Solved my own problem. The following bit of VBA does what I wanted.

Option Explicit
Option Base 1

Public Function myDiag(dDat As Variant) As Variant
Dim arraySize As Long
Dim v As Variant
Dim curRow As Long
Dim curCol As Long
arraySize = dDat.Count
ReDim v(arraySize, arraySize) As Variant
For curRow = 1 To arraySize
For curCol = 1 To arraySize
v(curRow, curCol) = 0
Next curCol
v(curRow, curRow) = dDat(curRow)
Next curRow
myDiag = v
End Function