# R/gwrr.est.R In gwrr: Fits geographically weighted regression models with diagnostic tools

#### Documented in gwrr.est

gwrr.est <-
function(form, locs, data, kernel="exp", bw=TRUE, rd=TRUE, cv.tol){   # User-called function
# Parse variables in formula to pass to function
lhs <- as.character(form)[2]
rhs <- as.character(form)[3]
rhs.v <- strsplit(rhs, " + ", fixed=TRUE)   # Returns a list with 1 first element, unknown 2 elements
n.l <- length(rhs.v[[1]])   # get number of x variables

# Create y vector and design matrix
db <- data
y <- db[,lhs]
N <- dim(db)[1]
X <- rep(1,N)   # Assume an intercept
for(i in 1:n.l) X <- cbind(X, db[,rhs.v[[1]][i]])

# Calculate pairwise distances
library(fields)
S <- rdist(locs)   # Assume Euclidean distance is appropriate for now

rmspe <- NA   # RMSPE for CV, return NA if bandwidth and ridge are input

# Check what should be estimated
if (bw==TRUE){   # Estimate kernel bandwidth
band.ub <- ceiling(max(S))
band.lb <- min(S) + 0.01 * band.ub   # Add a small amount to min(S) to have non-zero value; ad hoc
if(missing(cv.tol)){
lm1 <- lm(form, data=db)
lm.rmse <- gwr.rmse(y, lm1\$fitted.values)
cv.tol <- lm.rmse * 0.05    # Set CV tolerance as small % of RMSE from linear model; ad hoc
}
if (rd==TRUE){   # Estimate ridge parameter
lam.lb <- 0
lam.ub <- 2   # Set reasonable range for shrinkage parameter; ad hoc
lam.tol <- 0.01 * (lam.ub-lam.lb)
g.bw <- gwrr.bw.rd.cv(band.lb, band.ub, cv.tol, lam.lb, lam.ub, lam.tol, X, y, S, kernel)
bw <- g.bw\$phi
rd <- g.bw\$lambda
rmspe <- g.bw\$RMSPE
}
}

# Call estimation functions
g.beta <- gwrr.beta(bw, rd, X, y, S, N, kernel)
g.yhat <- gwr.yhat(g.beta, X)
g.rmse <- gwr.rmse(y, g.yhat)
g.rsquare <- gwr.rsquare(y, g.yhat)

# Return estimates
params <- list(bw, rd, rmspe, g.beta, g.yhat, g.rmse, g.rsquare)
names(params) <- c("phi", "lambda", "RMSPE", "beta", "yhat", "RMSE", "rsquare")
params
}

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gwrr documentation built on May 2, 2019, 7:07 a.m.