[groundwater] stop using pandas

lecture/mhs/groundwater/contourplots.py

 import matplotlib.pyplot as plt
 import numpy as np
-import pandas as pd
 
-#Instructions: First execute the `groundwater` test, a file called "contourfile.txt" will be written to the respective build-cmake folder. Within the build-cmake/.../groundwater folder you can then run the python script via e.g. `python3 contourPlots.py` to plot the contour and streamlines of the given problem.
+#Instructions: First execute the `groundwater` test, a file called "contourfile.txt" will be written to the respective build-cmake folder. Within the build-cmake/.../groundwater folder you can then run the python script via e.g. `python3 contourplots.py` to plot the contour and streamlines of the given problem.
 
 plt.rcParams.update({'font.size': 10})
 
@@ -27,12 +26,12 @@ cells = parameters.get("Cells").split()
 nx = int(cells[0])
 ny = int(cells[1])
 #read in the data which should be plotted
-myData = pd.read_csv('contourfile.txt') #choose the correct name of the data file
+dataField = np.genfromtxt('contourfile.txt', delimiter=',', dtype=None, names=True, encoding='utf-8')
 
 #-------PREPARING DATA FOR CONTOUR PLOT-------
-xArray = myData['x'].values #read in a pandas data column and immediately convert it to a numpy array
-yArray = myData['y'].values
-hArray = myData['h'].values
+xArray = dataField['x']
+yArray = dataField['y']
+hArray = dataField['h']
 #reshape input from a vector to a matrix
 x = xArray.reshape(ny,nx)
 xLinspace = x[0] # each row is the same, take the first
@@ -57,8 +56,8 @@ fig.savefig('isolineplot.png', dpi=300)
 
 #-------PREPARING DATA FOR STREAMLINE PLOT-------
 #read in the data for the streamlines
-vxArray = myData['v_x'].values #read in a pandas data column and immediately convert it to a numpy array
-vyArray = myData['v_y'].values
+vxArray = dataField['v_x']
+vyArray = dataField['v_y']
 #reshape velocity fields from a vector to a matrix
 vx = vxArray.reshape(ny,nx)
 vy = vyArray.reshape(ny,nx)