Technically the definition of the nat log of zero is actually an asymptote.
What does zero mean in your data? That is the key issue you must approach before modifying the information. If zero means "too small to measure but not likely zero," then you can do some decimal estimation or I think you can use a tobit model, but I'm not super familiar with those. X+1 or X+0.1 etc. is typically used with count data. However, if the data do not mean that, or are actually some form of ratios, then when y < z, the ln (y/z) will be negative, so when you add one, you will have a bunch of zeros that cause you to lose data! I vaguely recall something about right and left censored models or something. However, you better make sure, I'm pulling this out of somewhere smelly because this is something I read once and I don't remember where. But, maybe it will give you a place to start? Malcolm On Tue, Feb 11, 2014 at 11:56 PM, Jason Hernandez < [email protected]> wrote: > Some time ago, I inquired about ways to analyze percent cover data, and > one of the suggestions was to test for heterogeneity. The snag, however, > is that this requires multiplying each cell value by its natural log. My > data set has a lot of zero values, which are important to keep; but of > course there is no natural log of zero. Is there a way to adjust the > analysis to included these zero values? i have not managed to find > anything on this. > > Jason Hernandez > > -- Malcolm L. McCallum Department of Environmental Studies University of Illinois at Springfield Managing Editor, Herpetological Conservation and Biology "Nothing is more priceless and worthy of preservation than the rich array of animal life with which our country has been blessed. It is a many-faceted treasure, of value to scholars, scientists, and nature lovers alike, and it forms a vital part of the heritage we all share as Americans." -President Richard Nixon upon signing the Endangered Species Act of 1973 into law. "Peer pressure is designed to contain anyone with a sense of drive" - Allan Nation 1880's: "There's lots of good fish in the sea" W.S. Gilbert 1990's: Many fish stocks depleted due to overfishing, habitat loss, and pollution. 2000: Marine reserves, ecosystem restoration, and pollution reduction MAY help restore populations. 2022: Soylent Green is People! The Seven Blunders of the World (Mohandas Gandhi) Wealth w/o work Pleasure w/o conscience Knowledge w/o character Commerce w/o morality Science w/o humanity Worship w/o sacrifice Politics w/o principle Confidentiality Notice: This e-mail message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message.
