Added the new function int2padstr().

Using a combination of format() and gsub().
The purpose is to simplify looping through many datafiles
in a single report using for-loops.
A way was needed to "convert" the for-loop's counting variable
into a string of set length padded with zeroes.
This function fills that need.

common.R

@@ -3,6 +3,7 @@
 # Taha Ahmed, Jan 2011
 
 # CONTENTS
+# >>>> int2padstr
 # >>>> It2charge
 # >>>> ProvideSampleId
 # >>>> ConvertRefPot
@@ -14,6 +15,29 @@
 
 
 
+##################################################
+################## int2padstr ####################
+##################################################
+int2padstr <- function (ii, pchr, w) {
+   ## Description:
+   ##   Converts an integer or a vector of integers to
+   ##   a string padded with characters. 
+   ## Usage:
+   ##   int2padstr(ii, pchr, w)
+   ## Arguments:
+   ##     ii: integer or vector of integers
+   ##   pchr: a padding character (e.g., "0")
+   ##      w: width of the return string (an integer)
+   ##         Make sure to set the width longer than
+   ##         or equal to the length of the biggest integer.
+   ##         For example, if the integers (ii) are
+   ##         in the range 1 - 100, set w to at least 3.
+   ## Value:
+   ##   A character string or a vector of character strings
+   gsub(" ", pchr, formatC(ii, format="s", mode="character", width = w))
+}
+
+
 ##################################################
 ################### It2charge ####################
 ##################################################