I'm dealing with spatial data where the response variable is the gas concentration. In addition, I've the x,y-coordinate values, and another covariates. I'm thinking to fit a Gaussian random field model as follows:
$$ Z(s) = X(s) \beta + \epsilon(s) $$
where $ [Z(s) : s \in R^2]$, $X(s)$ is a set of p covariates associated with each site s, $\beta$ is a p-dimensional vector of coefficients. I already estimated the covariance function for the error term, but now I'm having trouble on how to proceed. I'm using R, but so far, unfortunately, I've not come across any package where I can include covariates in the model.
I'm still learning spatial statistics, so if you've any hint, I would truly appreciate it.