R/plot_cycles.R

In mikegerhardt/echem: Importing and manipulating data from Gamry potentiostats

#' Plot a set of constant-current charge-discharge cycles
#' 
#' This function takes a set of voltage vs. time curves from a cyclic 
#' charge-discharge experiment and plots them.
#' 
#' This function is designed to be used on data frames generated with 
#' \code{import_all_cc_cycles} and may not work otherwise. The function will 
#' return a ggplot object which can be modified with ggplot methods.
#' 
#' @param inputdf Data frame, typically generated with
#'   \code{import_all_cc_cycles}
#' @param cyclelist A sequence of cycle numbers to plot. For example, setting
#'   \code{cyclelist} to \code{3:6} will plot only cycles 3 through 6. Defaults
#'   to plot all cycles.
#' @author Mike Gerhardt
#' @return Returns a ggplot object containing all charge/discharge cycles 
#'   specified by \code{cyclelist}
#'   
#' @seealso \code{\link{import_all_cc_cycles}}
#' @export

plot_cycles <- function(inputdf, cyclelist = "all"){
  
  if(cyclelist != "all"){
    # Subsets the input data frame as directed by cyclelist
    cycledf <- inputdf[inputdf$cycle %in% cyclelist, ]
  } else cycledf <- inputdf
  # If no cyclelist argument is given, just plot all the cycles.
  
  cyclebreaker <- sapply(cycledf$type, 
                        function(x) if(x == "Charge") 0 else 0.5)
  cyclebreaks <- cyclebreaker + cycledf$cycle
  cycledf <- cbind(cycledf, cyclebreaks = cyclebreaks)
  
  cycleplot <- (ggplot(cycledf, aes(x = abs(Q), y = Vf, color = cycle,
                                    group = cyclebreaks))
                + theme_bw(24)
                + geom_line()
                + xlab("Charge (C)")
                + ylab("Cell Voltage (V)")
                + scale_color_continuous(name = "Cycle")
  )
  return(cycleplot)
}