I would like to request help for coding the lme for the following: Soils from 14 Regions (fixed) were sampled every Year (fixed) during three years. Each Year each Region was sampled at several Points (random), and two Cores (random) were taken at each Point. Each Core was split into five Depths (fixed, crossed with all other factors) and C (response) was measured at each Depth of each Core of each Point of each Region in each Year. First, I want to assume that Points were randomly selected each year, and I want to test an AR(1) over Depth. Second, I want to assume that Points were selected only once during the first year. Each near, new cores were randomly selected from each of the original points. I would like to test and AR(1) for year. Help will be greatly appreciated and knowledge will be passed on to other students. Thank you. PS: lme(C ~ Region*Year*Depth, data=soil, random=~1|Region/Point/Core) just returned: Error in MEEM(object, conLin, control$niterEM) : Singularity in backsolve at level 0, block 1 -- Emilio A. Laca One Shields Avenue, 2306 PES Building Agronomy and Range Science ealaca at ucdavis.edu University of California fax: (530) 752-4361 Davis, California 95616 (530) 754-4083