Using Regression Function in VBA Macro
"Martin Brown" wrote in message
On 28/05/2014 21:52, Peter T wrote:
"Martin Brown" wrote in message On
I know that's not a 'stressful' test but could you illustrate when Linest
becomes unreliable and/or returns different coeff's to a high precision
chart formula.
Add an offset of about 10000 to all the x values - this makes the
condition number of the problem much higher for a naive code. It is the
sort of thing that can happen when the x values are dates for example.
But is that a realistic scenario, 10000^5 is 10E+20 which would imply a
decimal cooefficient with at least 10 to 15 leading zeros.
When they first released XL2007 they broke the polynomial fit in charts to
make it agree with a well known PC package with the same defect!
In light testing I still can't reproduce any discrepancies.
Regards,
Peter T
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