sigmoid curve fitting in trend lines

[James Salsman <jsalsman@gmail.com>]

Rob Weir
Chair
OASIS Open Document Format for Office Applications (OpenDocument)
Technical Committee

Dear Mr. Weir:

True exponential curves do not actually exist in economics, biology,
or any other finite field. They are all sigmoid curves such as the
logistic or Gompertz curve. Offering users the ability to fit a trend
line to an exponential curve but not a logistic and Gompertz sigmoid
does them a disservice, and makes it much more likely that they will
make extrapolation errors.

Therefore, I request that you modify OASIS Standard
OpenDocument-v1.2-part1, Section 20.43, "chart:regression-type" [
http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part1.html#__RefHeading__1419514_253892949
] as follows:

At the end of the bulleted list under "The defined values for the
chart:regression-type attribute are:", please add:

"* logistic sigmoid – Regression with a logistic sigmoid function –
approximate the values of the series using the model: y =
A+B/(1+e^(-(x-C)/D))

"* Gompertz sigmoid – Regression with a logistic sigmoid function –
approximate the values of the series using the model: y =
A+B·e^(C·e^(D·x))"

Please let me know by email to jps-oasis-regression@talknicer.com if
you have any questions about this request. Thank you.

Best regards,
James Salsman

Ref.: https://bugs.freedesktop.org/show_bug.cgi?id=46539