def find_z(s, s_axis, x_range = [0,0], y_range = [0, -1]):
# determine the range to be plotted
x_min, x_max, y_min, y_max = P.find_axes(s_axis[2], s_axis[0], x_range, y_range)
# make the contours
# first find the area to be plotted
# not the most elegant way I guess
try:
y_min_i = numpy.where(s_axis[0] < y_min)[0][-1]
except:
y_min_i = 0
try:
y_max_i = numpy.where(s_axis[0] > y_max)[0][0]
except:
y_max_i = len(s_axis[0])
try:
x_min_i = numpy.where(s_axis[2] < x_min)[0][-1]
except:
x_min_i = 0
try:
x_max_i = numpy.where(s_axis[2] > x_max)[0][0]
except:
x_max_i = len(s_axis[2])
ma = numpy.amax(s[y_min_i:y_max_i, x_min_i:x_max_i])
mi = numpy.amin(s[y_min_i:y_max_i, x_min_i:x_max_i])
return ma, mi
