R/plot.R

In trafficonese/coinmarketcap_v2: Get Cryptocurrencies Market Cap Prices from Coin Market Cap

#' Plot The Price of the Largest Market Cap Cryptocurrencies
#'
#' @param currency currency code (default is 'USD')
#' @param k the number of top cryptocurrencies to plot (default is 5)
#' @param bar_color a valid color name or hexadecimal color code (default is 'grey')
#' @return A ggplot of top Cryptocurrencies based on their rank (Market Cap)
#' @examples
#' plot_top_currencies('EUR')
#' plot_top_currencies('GBP')
#' @export
plot_top_currencies <- function(currency = "USD", k = 5, bar_color = "grey") {

    stopifnot(currency %in% get_valid_currencies())

    k <- as.integer(k)
    if (k < 1)
        stop("Parameter k must be a integer value greater than zero.")

    temp <- data.frame(fromJSON(rawToChar(curl_fetch_memory(
        paste0("https://api.coinmarketcap.com/v1/ticker/?convert=",
               currency))$content)))

    if (k > nrow(temp))
        warning(paste0("The argument provided to k is greater than the ",
                       "number of cryptocurrencies. Only ", nrow(temp),
                       " will be plotted."))

    temp <- temp[seq_len(min(k, nrow(temp))), ]

    temp[, tolower(paste0("price_", currency))] <- round(
        as.numeric(temp[, tolower(paste0("price_", currency))]), 2)

    ggplot(temp, aes_string("name", tolower(paste0("price_", currency)))) +
        geom_bar(stat = "identity", fill = bar_color) +
        ylab(paste0("Price in ", currency)) +
        xlab("Cryptocurrencies") +
        ggtitle(paste0("Top ", k,
                       " Cryptocurrencies with Largest Marketcaps")) +
        coord_flip()
}