[rrd-developers] logarithmic functions

Peter Bailey temporary.212 at kidmillennium.net
Sun Nov 23 00:39:09 MET 2003

	The current logarithmic functions in rrdtool are limited to natural
	logs, which necessarily means no logs of base <1.

	I plan to implement a system allowing different logarithmic bases and
	hopefully adjust the autoscaler to make bring out the important parts
	(including manipulating the log base).

	Logarithmic plotting helps when you have exponential data, but it also
	helps when you have data with generally little change spiked by huge
	changes, and you don't want to cut the data from the huge changes.

	If anyone is or has worked on similar ideas, please let me know what's
	going on.

	I'm considering the best most intuitive ways to take information and
	which variables should be allowed:

		-logarithmic base (e, 10, 8, 2, 0.1, etc)

	also considering:
		-upper-exponent (not sure about this as it is syn with --upper-limit)
		-lower-exponent (-10, 0, 15--also syn with -lower-limit)

	I'm looking at trying to make an exponent autoscaler that would
	attempt to bring out the meaningful data.  It will find an appropriate
	base.  As the base gets closer to one, the scale gets closer to
	linear.  From 1 down to 0 it gets exponential in the opposite
	direction (i.e. instead of stretching data on the top of the graph, it
	will stretch the bottom).

	Another idea might be to use a varying function for the base that
	would stretch the top and the bottom or compress both.

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