#' @title Check the validity of an `fluvgeo` `flowline_points` data structure
#'
#' @description Checks that the input data structure `flowline_points` meets
#' the requirements for this data structure.
#'
#' @export
#' @param flowline_points sf object; a `flowline_points` data
#' structure used by the fluvgeo package.
#'
#' @return Returns TRUE if the `flowline_points` data structure matches the
#' requirements. The function throws an error for a data structure not matching
#' the data specification. Returns errors describing how the the data structure
#' doesn't match the requirement.
#'
#' @importFrom assertthat assert_that
#'
check_flowline_points <- function(flowline_points) {
name <- deparse(substitute(flowline_points))
# Check data structure
assert_that(class(flowline_points)[1] == "sf",
msg = paste(name, "must be a sf object"))
assert_that(is.data.frame(flowline_points),
msg = paste(name, "must be a data frame"))
assert_that("ReachName" %in% colnames(flowline_points) &
is.character(flowline_points$ReachName),
msg = paste("Character field 'ReachName' missing from ", name))
assert_that("POINT_X" %in% colnames(flowline_points) &
is.numeric(flowline_points$POINT_X),
msg = paste("Numeric field 'POINT_X' missing from ", name))
assert_that("POINT_Y" %in% colnames(flowline_points) &
is.numeric(flowline_points$POINT_Y),
msg = paste("Numeric field 'POINT_Y' missing from ", name))
assert_that("POINT_M" %in% colnames(flowline_points) &
is.numeric(flowline_points$POINT_M),
msg = paste("Numeric field 'POINT_M' missing from ", name))
assert_that("Z" %in% colnames(flowline_points) &
is.numeric(flowline_points$Z),
msg = paste("Numeric field 'Z' missing from ", name))
# Check the field `ReachName` is not empty
assert_that(nchar(unique(flowline_points$ReachName[1])) > 0,
msg = paste("Field `ReachName` is empty in", name))
# Check flowline is digitized from downstream end to upstream end
## Get min and max POINT_M value
m_min <- min(flowline_points$POINT_M)
m_max <- max(flowline_points$POINT_M)
## Calculate min and max z
m_min_z <- min(flowline_points[flowline_points$POINT_M == m_min, ]$Z)
m_max_z <- max(flowline_points[flowline_points$POINT_M == m_max, ]$Z)
## Check downstream end is a lower elevation than upstream end
assert_that(m_min_z < m_max_z,
msg = paste("The flowline used to create", name,
"is not digitized beginning at the downstream end."))
}
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