Fit polynomial rating curve

Usage

rc_poly(discharge, stage, ..., data = NULL, degree = 2, variance = var_none())

Arguments

discharge: <data-masking> Discharge: a vector, or an expression evaluated in data, such as a column name.
stage: <data-masking> Stage: a vector, or an expression evaluated in data, such as a column name.
...: Must be empty. Present so that every argument after it has to be named in full.
data: Optional data frame in which discharge and stage are evaluated.
degree: Polynomial degree; positive whole number. Default 2.
variance: How the variance of the gaugings about the curve is modelled: var_none() (or "none", the default), var_prop() (or "prop"), or var_spec() with the variances. See variance.

Value

An rc_poly object; see rating_curve for its contents. The coefficients are named b0, b1, ... by power of stage.

Examples

fit <- rc_poly(discharge, stage, data = thompson, degree = 2)
predict(fit, new_stage = c(1, 3, 6), conflev = 0.95)
#> # A tibble: 3 × 4
#>   stage   fit ci_lwr ci_upr
#>   <dbl> <dbl>  <dbl>  <dbl>
#> 1     1  244.   222.   266.
#> 2     3  835.   816.   855.
#> 3     6 2201.  2181.  2221.