An R function to create columns with sequential tide numbers (for whole tidal cycles, flood, and ebb tides)

number.tides.R

### Important note: I'm no longer maintaining this gist, since this code is incorporated into the
### VulnToolkit package.
### Because it's not being maintained, the code below might not work. The latest, updated version
### is available at: 
### https://github.com/troyhill/VulnToolkit/blob/master/R/number_tides.R



### function to number tides and insert tide numbers (for whole tidal cycles, flood, and ebb tides)
### in high-frequency dataset.
### Requires HL() function output, and initial dataset
### input arguments:
### "data": full water level dataframe
### "datetime": date/time column from full dataset (used as "time" argument in HL())
### "hl": high-low function output (https://gist.github.com/troyhill/5489261)
###
### Have a problem? Find a bug? Email [email protected]


number.tides <- function(data, datetime, hl) {

data$ht.ind <- ifelse(datetime %in% hl$time[hl$tide == "H"], 1, 0)
data$lt.ind <- ifelse(datetime %in% hl$time[hl$tide == "L"], 1, 0)

data$tide.no <- cumsum(data$lt.ind)  # number tidal cycles

# number the flood and ebb tides (include numbers *only* on flood and ebb tides)
data$ht.temp <- cumsum(data$ht.ind)
data$index <- c(1:nrow(data))

if(data$index[data$ht.temp == "1"][1] - data$index[data$tide.no == "1"][1] > 0){        # positive value: low tide first
  data$ebb.fld <- ifelse(data$ht.temp == data$tide.no, 1, 0)                            # 1 = ebb tide; 0 = flood tide
  } else { data$ebb.fld <- ifelse(data$ht.temp > data$tide.no, 1, 0)   
  }
    
data$fld.no <- ifelse(data$ebb.fld == 0, data$tide.no, NA)
data$ebb.no <- ifelse(data$ebb.fld == 1, data$tide.no, NA)

drop <- c("ht.temp", "index")
data <- data[, !(names(data) %in% drop)]

  invisible(data)
}