Error : Data is not an unmarkedFrameOccu object

[Bérénice Givord-Coupeau]

Hi everyone,

I'm a begginer in occupancy models, sorry if it's a silly question.

I'm trying to run a single-season occupancy models but I'm facing a difficulty.

Here's a part of what I did :

site.covs <- data.frame(A = data$grass_coverage, B = data$tree_coverage, C = data$presence_Zv) 

occu <- unmarkedFrameOccu(data, obsCovs = list(temperature, clouds, wind, duration), siteCovs = site.covs)

Models with obsCovs work just fine (for instance occu(~temperature, ~1, data)) but when I'm running models with siteCovs (occu (~1, ~ A, data)) I have the following error : 

Data is not an unmarkedFrameOccu object.

The number of site in site.covs match the data and here's what gave me str (site.covs) :

'data.frame': 41 obs. of  4 variables:

 $ Area : int  1 2 3 4 5 6 7 8 9 10 ...

 $ grass_coverage : num  73.9 60.1 58.3 59.8 68.3 ...

 $  tree_coverage : num  23.9 33.8 26 33.4 30.1 ...

 $ presence_Zv : int  1 1 1 1 0 0 0 0 1 1 ...

Also, do you know if it's possible to include all site covariables in a model?

I'm sure it's a very simple to fix but I can't figure out what's wrong.

Thank you a lot in advance,

Bérénice