LAB ASSIGNMENT 8 (due 04/02/14)
____________________________

(Total Points: 15)

	
	In Lab 8, item 7, we wrote the function COMPRESS1 which finds the
	M absolutely largest entries of a real or complex vector X, nulls out 
	the remaining entries, and also computes the energy (square norm) 
	ratio R between the output and input vectors.

	Write a variant of COMPRESS1, called COMPRESS2, which is called as
	follows:

		[Y,K,L,R] = compress2(X,M)

	The argument X is a complex 2-D array. As before, the M absolutely
	largest entries of X are selected, the remaining entries are nulled
	out, and the energy ratio

		R = (sum of |.|^2 of output array (Y) elements)/
			(sum of |.|^2 of input array (X) elements)

	is computed.  In addition, two output index vectors K and L are
	generated, such that

			[K L]

	consists of the M pairs of indices (k,l) such that X(k,l) is
	selected for Y.  The ordering of these index pairs should follow 
	the linear indexing convention in MATLAB, i.e., column-by-column.

	For example, if

	x = 

	    	-1     3     4     7
	     	 8    -2     1     1
	     	 0   -13     1     4
	
	and M = 5, then  

		[y,K,L,r] = compress2(x,M)

	should produce

	y = 

		0     0     4     7
		8     0     0     0
		0   -13     0     4
	
	and

	[K L] = 
	
	     2     1
	     3     2
	     1     3
	     1     4
	     3     4


	Hints:

	- Do NOT start your code in a function structure.  Instead, you should 
	  start with a piece of code that fulfills all the aforementioned 
	  requirements and eventually, if no error can be found, shape your 
	  code to the required function COMPRESS2.

	- Review the notation x(:) and study the function RESHAPE.

	- The function IND2SUB will be particularly useful in generating
	  the index vectors K and L.

________

Submit a zip or rar package containing the following files (use exact 
file names as shown):

lastname_labhw_08.m

	It should contain 

		- a matrix x defined in your favor for testing purpose,
		
		- a value M defined in your favor for testing purpose,

		- a piece of code that does what COMPRESS2 will do, and

		- useful comments.

compress2.m

	The required function.

The zip or rar package should be named as lastname_labhw_08.zip / .rar, and 
should be uploaded from the upload link on the course lab web page 
<http://terpconnect.umd.edu/~jzsimon/enee222/lab.html>, or if not possible, 
emailed to enee222S2013@gmail.com.