reach_height_lm: Weighted linear model for height as a function of distance...
In markwh/rivertile: R interface for SWOT rivertile data

Used for computing reach-level heights and slopes with corresponding uncertainty.

1 2	reach_height_lm(node_h, node_h_u, node_x, x_ctr, loc_offset, weight = TRUE)

`node_h`	Vector of node heights
`node_h_u`	Vector of node height uncertainty (1-sigma)
`node_x`	Vector of node downstream distance
`x_ctr`	center of reach, as given by meandist in `add_offset()`
`loc_offset`	From reach-level rivertile, distance from observed to prior reach center
`weight`	Use weighted least-squares? Default is TRUE.