From 5a5f3133d3b6a0c78bcfde76ee0ad1f2d92b15e1 Mon Sep 17 00:00:00 2001
From: Taha Ahmed <taha@mkem150>
Date: Thu, 10 Feb 2011 12:02:00 +0100
Subject: [PATCH] Two new functions in common.R

Celsius2Kelvin()
Kelvin2Celsius()

Including very crude error checks (checks that supplied temperature
is not below absolute zero, if so, sets it to absolute zero).
Idea: would be nice if function returned same number of significant
digits as it received.
---
 common.R | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/common.R b/common.R
index 74b1909..b71ef03 100755
--- a/common.R
+++ b/common.R
@@ -1,7 +1,78 @@
+# common.R
+# General-purpose functions
+# Taha Ahmed, Jan 2011
+
+# CONTENTS
+# >>>> Celsius2Kelvin
+# >>>> Kelvin2Celsius
+# >>>> as.radians
+# >>>> as.degrees
+# >>>> molarity2mass
+
+
+
+
+##################################################
+############### Celsius2Kelvin ###################
+##################################################
+Celsius2Kelvin <- function(Celsius) {
+   # Converts temperature from Celsius to Kelvin
+   #
+   # Check and correct for values below -273.15
+   if (Celsius < -273.15) {
+      # If Celsis is less than absolute zero, set it to absolute zero
+      Celsius <- -273.15
+   }
+   Kelvin <- Celsius + 273.15
+}
+
+
+##################################################
+############### Kelvin2Celsius ###################
+##################################################
+Kelvin2Celsius <- function(Kelvin) {
+   # Converts temperature from Kelvin to Celsius
+   #
+   # Check and correct for negative values
+   if (Kelvin < 0) {
+      # If Kelvin is less than zero, set it to zero
+      Kelvin <- 0
+   }
+   Celsius <- Kelvin - 273.15
+}
+
+
+##################################################
+################# as.radians #####################
+##################################################
 as.radians <- function(degrees) {
+   # Converts from degrees to radians
    radians <- degrees * (pi / 180)
 }
 
+
+##################################################
+################# as.degrees #####################
+##################################################
 as.degrees <- function(radians) {
+   # Converts from radians to degrees
    radians <- radians * (180 / pi)
 }
+
+
+##################################################
+############### molarity2mass ####################
+##################################################
+molarity2mass <- function(formulamass, volume, molarity) {
+   # Calculates the required mass of
+   # the substance to be dissolved.
+   # ARGS: formulamass - formula mass of the substance (in gram per mole)
+   #       volume      - volume of the final solution (in liters)
+   #       molarity    - molarity (in moles per liter)
+   # VALUE: mass of substance (in grams)
+   #
+   mass <- formulamass * volume * molarity 
+   # Unit check:
+   # [g * mol-1] * [liter] * [mole * liter-1] = [g]
+   return(mass)
+}