Exponentials 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. Here is how to do it in R: http://thebiobucket.blogspot.com/2011/04/fit-sigmoid-curve-with-confidence.html and Matlab/Octave: http://www.mathworks.com/matlabcentral/newsreader/view_thread/169459 Thank you.

The current standard ODF1.2 specifies only that kind of curves, which are implemented already. To get new kind of regression curves a addition to the standard is needed. Can you write a proposal to OASIS? It need not contain the algorithm but a reference to the mathematical definition is needed. There have already been proposals for new kind of regression curves, so it is likely that additional types are possible for ODF1.3

(In reply to comment #1) > The current standard ODF1.2 specifies only that kind of curves, which are > implemented already. To get new kind of regression curves a addition to the > standard is needed. Can you write a proposal to OASIS? It need not contain the > algorithm but a reference to the mathematical definition is needed. Regina, I am very happy to do so, but please send me the URL to instructions if any, or at least the sub-organization involved, and email address(es) if you have them. As for the mathematical definition, please see: http://en.wikipedia.org/wiki/Logistic_function and http://en.wikipedia.org/wiki/Gompertz_function

(In reply to comment #1) > Can you write a proposal to OASIS? Regina, I understand that I need to request a change to http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part1.html#__RefHeading__1419514_253892949 but where do I send that request?

[done:] Date: Thu, 23 Feb 2012 19:05:44 -0700 Subject: sigmoid curve fitting in trend lines From: James Salsman <jsalsman@gmail.com> To: robert_weir@us.ibm.com, office-comment@lists.oasis-open.org 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 =E2=80=93 Regression with a logistic sigmoid function = =E2=80=93 approximate the values of the series using the model: y =3D A+B/(1+e^(-(x-C)/D)) "* Gompertz sigmoid =E2=80=93 Regression with a logistic sigmoid function = =E2=80=93 approximate the values of the series using the model: y =3D A+B=C2=B7e^(C=C2=B7e^(D=C2=B7x))" 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=3D46539

Well, that looks terrible pasted into bugzilla. The two lines in question are: "* 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))"

(In reply to comment #5) >... > "* Gompertz sigmoid – Regression with a logistic sigmoid function – s/logistic/Gompertz/ on that line. Sorry.