Functions to automate downloading data from the Government of Canada's Climate/Weather website

genURLS.R

genURLS <- function(id, start, end, timeframe = c("hourly", "daily", "monthly")) {
    years <- seq(start, end, by = 1)
    nyears <- length(years)
    timeframe <- match.arg(timeframe)
    if (isTRUE(all.equal(timeframe, "hourly"))) {
        years <-  rep(years, each = 12)
        months <- rep(1:12, times = nyears)
        ids <- rep(id, nyears * 12)
    } else if (isTRUE(all.equal(timeframe, "daily"))) {
        months <- 1                      # this is essentially arbitrary & ignored if daily
        ids <- rep(id, nyears)
    } else {
        years <- start                   # again arbitrary, for monthly it just gives you all data
        months <- 1                      # and this is also ignored
        ids <- id
    }
    timeframe <- match(timeframe, c("hourly", "daily", "monthly"))
    URLS <- paste0("http://climate.weather.gc.ca/climate_data/bulk_data_e.html?stationID=", id,
                   "&Year=", years,
                   "&Month=", months,
                   "&Day=14",
                   "&format=csv",
                   "&timeframe=", timeframe,
                   "&submit=%20Download+Data"## need this stoopid thing as of 11-May-2016
                   )
    list(urls = URLS, ids = ids, years = years, months = rep(months, length.out = length(URLS)))
}

getData.R

getData <- function(stations, folder, timeframe = c("hourly", "daily", "monthly"), verbose = TRUE, delete = TRUE) {
    timeframe <- match.arg(timeframe)
    ## form URLS
    urls <- lapply(seq_len(NROW(stations)),
                   function(i, stations, timeframe) {
                       genURLS(stations$StationID[i],
                               stations$start[i],
                               stations$end[i], timeframe = timeframe)
                   }, stations = stations, timeframe = timeframe)

    ## check the folder exists and try to create it if not
    if (!file.exists(folder)) {
        warning(paste("Directory:", folder,
                      "doesn't exist. Will create it"))
        fc <- try(dir.create(folder))
        if (inherits(fc, "try-error")) {
            stop("Failed to create directory '", folder,
                 "'. Check path and permissions.", sep = "")
        }
    }

    ## Extract the data from the URLs generation
    URLS <- unlist(lapply(urls, '[[', "urls"))
    sites <- unlist(lapply(urls, '[[', "ids"))
    years <- unlist(lapply(urls, '[[', "years"))
    months <- unlist(lapply(urls, '[[', "months"))

    ## filenames to use to save the data
    fnames <- paste(sites, years, months, "data.csv", sep = "-")
    fnames <- file.path(folder, fnames)

    nfiles <- length(fnames)

    ## set up a progress bar if being verbose
    if (isTRUE(verbose)) {
        pb <- txtProgressBar(min = 0, max = nfiles, style = 3)
        on.exit(close(pb))
    }

    out <- vector(mode = "list", length = nfiles)
    hourlyNames <- c("Date/Time", "Year", "Month","Day", "Time", "Data Quality",
                     "Temp (degC)", "Temp Flag", "Dew Point Temp (degC)",
                     "Dew Point Temp Flag", "Rel Hum (%)", "Rel Hum Flag",
                     "Wind Dir (10s deg)", "Wind Dir Flag", "Wind Spd (km/h)",
                     "Wind Spd Flag", "Visibility (km)", "Visibility Flag",
                     "Stn Press (kPa)", "Stn Press Flag", "Hmdx", "Hmdx Flag",
                     "Wind Chill", "Wind Chill Flag", "Weather")
    dailyNames <- c("Date/Time", "Year", "Month", "Day", "Data Quality", "Max Temp (degC)", "Max Temp Flag",
                    "Min Temp (degC)", "Min Temp Flag", "Mean Temp (degC)", "Mean Temp Flag",
                    "Heat Deg Days (degC)", "Heat Deg Days Flag", "Cool Deg Days (degC)", "Cool Deg Days Flag",
                    "Total Rain (mm)", "Total Rain Flag", "Total Snow (cm)", "Total Snow Flag",
                    "Total Precip (mm)", "Total Precip Flag", "Snow on Grnd (cm)", "Snow on Grnd Flag",
                    "Dir of Max Gust (10s deg)", "Dir of Max Gust Flag", "Spd of Max Gust (10s deg)", "Spd of Max Gust Flag")
    monthlyNames <- c("Date/Time", "Year", "Month",
                      "Mean Max Temp (degC)", "Mean Max Temp Flag",
                      "Mean Min Temp (degC)", "Mean Min Temp Flag",
                      "Mean Temp (degC)", "Mean Temp Flag",
                      "Extr Max Temp (degC)", "Extr Max Temp Flag",
                      "Extr Min Temp (degC)", "Extr Min Temp Flag",
                      "Total Rain (mm)", "Total Rain Flag",
                      "Total Snow (cm)", "Total Snow Flag",
                      "Total Precip (mm)", "Total Precip Flag",
                      "Snow Grnd Last Day (cm)", "Snow Grnd Last Day Flag",
                      "Dir of Max Gust (10s deg)", "Dir of Max Gust Flag",
                      "Spd of Max Gust (10s deg)", "Spd of Max Gust Flag")

    cnames <- switch(timeframe, hourly = hourlyNames, daily = dailyNames, monthly = monthlyNames)
    TIMEFRAME <- match(timeframe, c("hourly", "daily", "monthly"))
    SKIP <- c(16, 25, 18)[TIMEFRAME]

    for (i in seq_len(nfiles)) {
        curfile <- fnames[i]

        ## Have we downloaded the file before?
        if (!file.exists(curfile)) {    # No: download it
            dload <- try(download.file(URLS[i], destfile = curfile, quiet = TRUE))
            if (inherits(dload, "try-error")) { # If problem, store failed URL...
                out[[i]] <- URLS[i]
                if (isTRUE(verbose)) {
                    setTxtProgressBar(pb, value = i) # update progress bar...
                }
        next                             # bail out of current iteration
            }
        }

        ## Must have downloaded, try to read file
        ## skip first SKIP rows of header stuff
        ## encoding must be latin1 or will fail - may still be problems with character set
        cdata <- try(read.csv(curfile, skip = SKIP, encoding = "latin1", stringsAsFactors = FALSE), silent = TRUE)

        ## Did we have a problem reading the data?
        if (inherits(cdata, "try-error")) { # yes handle read problem
            ## try to fix the problem with dodgy characters
            cdata <- readLines(curfile) # read all lines in file
            cdata <- iconv(cdata, from = "latin1", to = "UTF-8")
            writeLines(cdata, curfile)          # write the data back to the file
            ## try to read the file again, if still an error, bail out
            cdata <- try(read.csv(curfile, skip = SKIP, encoding = "UTF-8", stringsAsFactors = FALSE), silent = TRUE)
            if (inherits(cdata, "try-error")) { # yes, still!, handle read problem
                if (delete) {
                    file.remove(curfile) # remove file if a problem & deleting
                }
                out[[i]] <- URLS[i]    # record failed URL...
                if (isTRUE(verbose)) {
                    setTxtProgressBar(pb, value = i) # update progress bar...
                }
                next                  # bail out of current iteration
            }
        }

        ## Must have (eventually) read file OK, add station data
        cdata <- cbind.data.frame(StationID = rep(sites[i], NROW(cdata)),
                                  cdata)
        names(cdata)[-1] <- cnames
        out[[i]] <- cdata

        if (isTRUE(verbose)) { # Update the progress bar
            setTxtProgressBar(pb, value = i)
        }
    }

    out                                 # return
}

The latest version fixes a bug in which the genURLS() function was creating too many URLs for daily and monthly downloads because I'd misunderstood what was in each file.

There was also an incorrect column name in the monthlyNames list.

I'm getting a consistent error regarding names:

> library("canadaHCD")
> find_station("Victoria Harbour A")
# A tibble: 3 x 5
                Name         Province StationID LatitudeDD LongitudeDD
              <fctr>           <fctr>    <fctr>      <dbl>       <dbl>
1 VICTORIA HARBOUR A British Columbia     10944      48.42     -123.39
2 VICTORIA HARBOUR A British Columbia     53478      48.42     -123.39
3 VICTORIA HARBOUR A British Columbia     53479      48.42     -123.39
> StationID
Error: object 'StationID' not found
> vha <- hcd_monthly(10944)
  |                                                               |   0%Parsed with column specification:
cols(
  `Station Name` = col_character(),
  `VICTORIA HARBOUR A` = col_character()
)
Error in names(df) <- if (inherits(df[[1]], "Date")) { : 
  'names' attribute [23] must be the same length as the vector [2]

Any update on this?