R help - Sep 2011 - create loops in the explanatory variables using lm

Hi everyone

I am new to the list and read all the instructions, hope i get it right.

I have the following linear model:


model_sqrt<-lm(sqrt(mortality)~richness
               +Acer_davidii+Ailanthus_altissima+Alniphyllum_fortunei
               +Betula_luminifera+Castanea_henryi+Castanopsis_carlesii
               +Castanopsis_eyrei+Castanopsis_fargesii+Castanopsis_sclerophylla
               +Celtis_biondii+Choerospondias_axillaris+Cinamomum_camphora
              
+Cyclobalanopsis_glauca+Cyclobalanopsis_myrsinifolia+Diospyros_glaucifolia
              
+Elaeocarpus_chinensis+Elaeocarpus_glabripetalus+Elaeocarpus_japonicus
               +Idesia_polycarpa+Koelreuteria_bipinnata+Liquidambar_formosana
               +Lithocarpus_glaber+Machilus_grijsii+Machilus_leptophylla
              
+Machilus_thunbergii+Manglietia_yuyuanensis+Melia_azedarach+Meliosma_flexuosa
               +Nyssa_sinensis+Phoebe_bournei+Quercus_acutissima+Quercus_fabri
              
+Quercus_phillyreoides+Quercus_serrata+Rhus_chinensis+Sapindus_mukorossi
               +Sapium_discolor+Sapium_sebiferum+Schima_superba
	       +community
,weights=wei)




Where everything from Acer_davidii to Schima_superba are plant species. Since
the order of the plant species matters in my case, I want to repeatedly fit the
model so that every species is in the first place, that is after the richness
term, once.

I am looking for a way so that I don't have to do this by hand. I already
checked combn with as.formula and paste, but I couldn't get it right.

I'd be very grateful for any help.


Thanks


David


	[[alternative HTML version deleted]]

Hi

Well, are those names (Acer_davidii, ...) columns in data frame? If not 
and you want them as factors of species you shall reformat your input so 
as you get data frame with columns mortality, richness, species, 
community. Column species shall have your plant species names in each 
respective row.

Your lm call shall be

lm(sqrt(mortality)~richness+species+community, data=your.data.frame)

see then

?relevel for setting reference level of your factor.

Regards
Petr

> 
> Hi everyone
> 
> I am new to the list and read all the instructions, hope i get it right.
> 
> I have the following linear model:
> 
> 
> model_sqrt<-lm(sqrt(mortality)~richness
>                +Acer_davidii+Ailanthus_altissima+Alniphyllum_fortunei
>                +Betula_luminifera+Castanea_henryi+Castanopsis_carlesii
> +Castanopsis_eyrei+Castanopsis_fargesii+Castanopsis_sclerophylla
> +Celtis_biondii+Choerospondias_axillaris+Cinamomum_camphora
>                +Cyclobalanopsis_glauca+Cyclobalanopsis_myrsinifolia
> +Diospyros_glaucifolia
>                +Elaeocarpus_chinensis+Elaeocarpus_glabripetalus
> +Elaeocarpus_japonicus
> +Idesia_polycarpa+Koelreuteria_bipinnata+Liquidambar_formosana
>                +Lithocarpus_glaber+Machilus_grijsii+Machilus_leptophylla
> +Machilus_thunbergii+Manglietia_yuyuanensis+Melia_azedarach
> +Meliosma_flexuosa
> +Nyssa_sinensis+Phoebe_bournei+Quercus_acutissima+Quercus_fabri
>                +Quercus_phillyreoides+Quercus_serrata+Rhus_chinensis
> +Sapindus_mukorossi
>                +Sapium_discolor+Sapium_sebiferum+Schima_superba
>           +community
> ,weights=wei)
> 
> 
> 
> 
> Where everything from Acer_davidii to Schima_superba are plant species. 
> Since the order of the plant species matters in my case, I want to 
> repeatedly fit the model so that every species is in the first place, 
that
> is after the richness term, once.
> 
> I am looking for a way so that I don't have to do this by hand. I 
already 
> checked combn with as.formula and paste, but I couldn't get it right.
> 
> I'd be very grateful for any help.
> 
> 
> Thanks
> 
> 
> David
> 
> 
>    [[alternative HTML version deleted]]
> 
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