POTENTIAL FIELD FOR THE ELECTRIC LENSE 1  (see script for the exercise, task 1):

 332.55  665.73    0.00    0.00    0.00    0.00 
 330.81  663.30    0.00    0.00    0.00    0.00 
 326.34  654.86    0.00    0.00    0.00    0.00 
 315.96  618.66  874.16  957.73  985.83  995.68 
 311.38  604.41  840.49  941.87  979.82  993.76 


THIS MATRIX HAS TO BE TRANSFERRED INTO A BIGGER MATRIX IN THE FOLLOWING WAY:

 ==> CORRECT MATRIX FOR THE CONTOUR-PLOT

   0.00    0.00    0.00    0.00 -665.73 -332.55    0.00  332.55  665.73    0.00    0.00    0.00    0.00 
   0.00    0.00    0.00    0.00 -663.30 -330.81    0.00  330.81  663.30    0.00    0.00    0.00    0.00 
   0.00    0.00    0.00    0.00 -654.86 -326.34    0.00  326.34  654.86    0.00    0.00    0.00    0.00 
-995.68 -985.83 -957.73 -874.16 -618.66 -315.96    0.00  315.96  618.66  874.16  957.73  985.83  995.68 
-993.76 -979.82 -941.87 -840.49 -604.41 -311.38    0.00  311.38  604.41  840.49  941.87  979.82  993.76 
-995.68 -985.83 -957.73 -874.16 -618.66 -315.96    0.00  315.96  618.66  874.16  957.73  985.83  995.68 
   0.00    0.00    0.00    0.00 -654.86 -326.34    0.00  326.34  654.86    0.00    0.00    0.00    0.00 
   0.00    0.00    0.00    0.00 -663.30 -330.81    0.00  330.81  663.30    0.00    0.00    0.00    0.00 
   0.00    0.00    0.00    0.00 -665.73 -332.55    0.00  332.55  665.73    0.00    0.00    0.00    0.00 


YOU CAN USE THIS MATRIX NOW E.G. IN A EASY MATLAB PLOT ROUTINE:
===============================================================

   drawing=load('matrix.dat');

   contour(drawing,20);
   axis off;
   axis('square');
   title('NUMERIK UEBUNG 2  ELEKTRISCHE LINSE 1');