[R] fields package question

[M P]

Hello,
I used commands below to obtain a surface, can plot it and all looks as
expected.
How do I evaluate values at new point. I tried as below but that produces
errors.
Thanks for suggestions/help.

x <- log(lambda)
y <- rh
z <- qext[,,2]

grid.l <- list(abcissa=x,ordinate=y)
xg <- make.surface.grid(grid.l)
out.p <- as.surface(xg,z)
plot.surface(out.p,type="p")

tried:
grid_new.l <- list(abcissa=c(-15.0,-10.),ordinate=y)
xg_new <- make.surface.grid(grid_new.l)

out_new.p <- predict.surface(out.p,xg_new)

results in this prompt:
predict.surface is now the function predictSurface>

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