From c810ef66bab65a8126714723d007dd2312896cbb Mon Sep 17 00:00:00 2001
From: Taha Ahmed <taha@txps>
Date: Tue, 15 Mar 2011 23:11:51 +0100
Subject: [PATCH] Updated It2charge() and fixed the relevant parts of
 amperometry2df().

It2charge() is now explicitly meant to be used only from within
other functions, such as amperometry2df().
---
 CHI.R    |  5 +----
 common.R | 31 +++++++++++++++++++++----------
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/CHI.R b/CHI.R
index 10413f6..82a187f 100644
--- a/CHI.R
+++ b/CHI.R
@@ -298,10 +298,7 @@ amperometry2df <- function(datafilename, wearea = 1) {
    ff <- cbind(ff, currentdensity = currentdensity)
    # Calculate charge densities and differentials
    charge.df <- It2charge(ff$currentdensity, ff$time)
-   ff <- cbind(ff, timediff = charge.df$timediff, 
-      chargedensity = charge$charge, 
-      sumchargedensity = charge$sumcharge, 
-      dQdt = charge$dQdt)
+   ff <- cbind(ff, charge.df)
    #
    ### Collect attributes of this experiment
    # These attributes are specific for each kind of experiment,
diff --git a/common.R b/common.R
index f63d6fa..3d20cf8 100644
--- a/common.R
+++ b/common.R
@@ -17,11 +17,22 @@
 ##################################################
 ################### It2charge ####################
 ##################################################
-It2charge <- function (current, time) {
-   ## Calculates charge etc. for amperometric data
-   ## current may be a current or a current density
-   ## (up to the calling function to keep track of which it is)
-   # Calculate the difference of the time vector
+It2charge <- function (time, current) {
+   ## Description:
+   ##    Calculates cumulative charge, differentials, etc. from
+   ##    amperometric data (current and time).
+   ##    __Intended to be used from within other functions (CHI.R)__
+   ## Usage:
+   ##    It2charge(time, current)
+   ## Arguments:
+   ##       time: a vector with time data.
+   ##    current: a vector of the same length as time, with current data.
+   ##             May be either currents or current densities, no matter.
+   ## Value:
+   ##    Returns a dataframe with columns:
+   ##    timediff, dIdt, charge, sumcharge
+   #
+   # Calculate the time vector difference
    timediff <- c(time[1], diff(time))
    # timediff times the current gives the charge,
    # since the time vector can be considered as
@@ -29,11 +40,11 @@ It2charge <- function (current, time) {
    # the current with the time elapsed since the last 
    # current measurement (the timediff).
    charge <- current * timediff
-   differential <- cumsum(charge) / time
-   # Prepare the return dataframe
-   ff <- data.frame(time = time, timediff = timediff, 
-      current = current, charge = charge, 
-      sumcharge = cumsum(charge), dQdt = differential)
+   dIdt <- current / time
+   # Return value
+   ff <- data.frame(timediff = timediff, 
+      dIdt = dIdt, charge = charge, 
+      sumcharge = cumsum(charge))
    return(ff)
 }