Projection matrices with fit=FALSE

andy.R

library(mgcv)
set.seed(2) ## simulate some data...
dat <- gamSim(1,n=400,dist="normal",scale=2)
b <- gam(y~s(x1), data=dat, fit=FALSE)

newpred <- data.frame(x1=seq(0, 10, length.out=100))

# Lp for the data
lp_data <- PredictMat(b$smooth[[1]], dat)

# same? (ignore intercept)
all.equal(b$X[,-1], lp_data, check.attributes=FALSE)


# compare to actually fitting the model
bfit <- gam(y~s(x1),data=dat)

lp_data_fit <- predict(bfit, dat, type="lpmatrix")

# need to drop first column (intercept!)
all.equal(lp_data_fit[,-1], lp_data, check.attributes=FALSE)


# Lp for prediction grid

# unfit
lp_pred <- PredictMat(b$smooth[[1]], newpred)
# fit
lp_pred_fit <- predict(bfit, newpred, type="lpmatrix")

# same?
all.equal(lp_pred_fit[,-1], lp_pred, check.attributes=FALSE)