Find key features of a spell including and ordered spell ID and each spell's duration

spell_features.R

#' Find key features of a spell including and ordered spell ID and each spell's
#' duration 
#' 
#' @param x a time ordered vector with values identifying a spell. It is 
#' assumed that when a value in this vector changes that the spell has ended.
#' @param id logical specifying whether or not to return the spell ID
#' @param duration logical specifying whether or not to return the spell 
#' duration. 
#' 
#' @examples 
#' # Create fake data
#' x <- c('a', 'a', 'a', 'a', 'b', 'b', 'b', 'c', 'a', 'a')
#' Find spell features
#' spell_features(x)
#' 
#' @importFrom dplyr %>% group_by mutate
#' 
#' @export

spell_features <- function(x, id = TRUE, duration = TRUE) {
    require(dplyr)
    message('Assumption: x is in the correct time order.\n')
    
    temp <- data.frame(x = x, x1 = c(NA, x[-length(x)]))

    # Find spell ID
    temp$spell_id[is.na(temp$x1)] <- 1

    for (i in 2:nrow(temp)) {
        if (temp[i, 1] == temp[i, 2]) temp[i, 3] <- temp[(i - 1), 3]
        else temp[i, 3] <- temp[(i - 1), 3] + 1
    }
    
    # Find spell duration
    if (isTRUE(duration)) {
        temp$fake <- 1
        temp <- temp %>% group_by(spell_id) %>% mutate(duration = cumsum(fake))
        temp <- as.data.frame(temp)
    }
    
    if (isTRUE(id) & isTRUE(duration)) {
        out <- temp[, c('spell_id', 'duration')]
    } 
    else if (!isTRUE(duration)) {
        out <- temp[, 'spell_id']
    }
    else if (!isTRUE(id)) {
        out <- temp[, 'duration']
    }
    return(out)
}