rtide: Tide Heights

# Abram Fleishman
# Conservation Metrics Inc
# www.conservationmetrics.com
# 10 Jan 2016
# abram AT conservationmetrics.com

# use rvest to scrape station info from NOAA site
library(stringr)
library(dplyr)
library(rvest)
library(rtide)
library(magrittr)

noaa_tide <- read_html("https://tidesandcurrents.noaa.gov/tide_predictions.html")
a <- noaa_tide %>%
  html_nodes(xpath = "//table//td//a") %>%
  html_attrs()
dataOut <- NULL
head(a)
# get info for each tide station then subset for subordinate stations only
for (i in seq_along(a)) {
  noaa_tide_temp <- read_html(paste0("https://tidesandcurrents.noaa.gov/tide_predictions.html", a[i]))
  b <- noaa_tide_temp %>%
    html_nodes("table") %>%
    html_table()
  b <- b[[1]][b[[1]]$Predictions != "&nbsp", ]
  head(b)

  bb <- noaa_tide_temp %>%
    html_nodes(xpath = "//table//tr//td/a") %>%
    html_attrs()
  b$path <- (unlist(bb))
  bb <- b[b$Predictions == "Harmonic", ]

  bb$Id <- as.character(bb$Id)
  bb$Lat <- as.character(bb$Lat)
  bb$Lon <- as.character(bb$Lon)

  dataOut <- bind_rows(dataOut, bb)
}

head(dataOut)
dataOut$Name <- gsub("&nbsp", "", dataOut$Name)
dataOut <- dataOut[!duplicated(dataOut), ]
harmonic_stations <- dataOut

harmonic_stations$Lat <- as.numeric(gsub("+", "", harmonic_stations$Lat))
harmonic_stations$Lon <- as.numeric(gsub("+", "", harmonic_stations$Lon))

rhar <- rtide::harmonics$Station
rhar_full <- rtide::harmonics$Node
# loop through the rtide::harmonics$Station data and match latitude and longitude to the data from the noaa site.
# I had to round the lat/lon values when matching to 3 decimals because the same site in some cases were off by a little
rhar$Id <- NA
for (i in seq_len(nrow(rhar))) {
  rhar$Id[round(rhar$Longitude, 3) == round(harmonic_stations$Lon[i], 3) &
    round(rhar$Latitude, 3) == round(harmonic_stations$Lat[i], 3)] <- harmonic_stations$Id[i]
}

head(rhar)

table(unique(stations$ref_station_id) %in% rhar$Id)
table(is.na(rhar$Id))

stations[stations$ref_station_id == "9751401", ]
harmonic_stations[harmonic_stations$Id == "9751401", ]

# Save
saveRDS(harmonic_stations, "D:/harmonic_stations.rda")
saveRDS(rhar, "D:/new_harmonic_with_ref_id.rda")