[R-meta] setting certain covariances to 0 for the random LHS term

Dear Wolfgang and others,


In my current model I have the following random structures: (treatment | site) and (treatment | site.time), i.e. random variance across site and across time-within-site for the different treatments.

Treatments here are defined as (1) control, (2) mineral input MR, (3) organic input OR, and (4) combined mineral and organic input ORMR.

Now I extend the number of treatments by the organic input sources, i.e. control, MR, ORone, ORtwo, ORthree, ORMRone, ORMRtwo, ORMRthree etc.

I wish to know the variances for each of these extended treatments, but I don?t want to see covariances between combinations of organic input sources, only with Control (and MR). Is it possible to let the model know that, by setting these to 0 somehow?

Thanks!



Gil Gram
PhD researcher  |  Natural resource management/CCAFS
International Institute of Tropical Agriculture (IITA)
East African Hub/Kampala/Country office
Address: IITA-Uganda Plot 15B, Naguru East Road. P.O Box 7878, Kampala
Mobile: +256 755 315236  |  Belgium Mobile: +32 484 981200
Skype: gil.gram