R/mkMatUtil.R

In spNNGP: Spatial Regression Models for Large Datasets using Nearest Neighbor Gaussian Processes

parseFormula <-  function(formula, data, intercept=TRUE, justX=FALSE){
    
    # extract Y, X, and variable names for model formula and frame
    mt <- terms(formula, data=data)
    if(missing(data)) data <- sys.frame(sys.parent())
    mf <- match.call(expand.dots = FALSE)
    mf$intercept <- mf$justX <- NULL
    mf$drop.unused.levels <- TRUE
    mf[[1]] <- as.name("model.frame")
    mf <- eval(mf, sys.frame(sys.parent()))
    if (!intercept){
      attributes(mt)$intercept <- 0
    }

    # null model support
    X <- if (!is.empty.model(mt)) model.matrix(mt, mf)
    X <- as.matrix(X)         # X matrix
    xvars <- dimnames(X)[[2]] # X variable names
    xobs  <- dimnames(X)[[1]] # X observation names
    if (justX){
      Y <- NULL
    }
    else {
      Y <- as.matrix(model.response(mf, "numeric")) # Y matrix
    }
    return(list(Y, X, xvars, xobs))
  }