GNOME Bugzilla – Bug 633735
Exponential fit in graphs is flawed for small values.
Last modified: 2010-11-01 20:06:08 UTC
Originally reported as https://bugs.launchpad.net/ubuntu/+source/libio-digest-perl/+bug/599534. The exponential fit is broken in graphs. Using the following data plot A B 0.000568 0.22 0.001136 0.05 0.00170 0.02 0.000136 0.97 0.000329 0.42 Plot and add a trend-line. Make the trend-line exponential and you get a garbage fit. If you multiply column A by 4, the fit works. Multiply by 3 and it fails. It appears that the algorithm used for this type of trend-line is flawed and has limitations that do not occur in MS Excel. Actually, logest returns 0 as m1 coefficient because the actual result is too small to be represented as a double. The solution is to have a regression procedure returning the logarithms of the coefficients instead of the coefficients.
This problem has been fixed in our software repository. The fix will go into the next software release. Thank you for your bug report.