FIX: Make matplotlib an optional import

Only import it when needed in the plotting routines. It shouldn't
be a hard dependency, but when one would `import bezpy` before it
would be required because of the imports being in general modules.

bezpy/__init__.py

@@ -6,17 +6,4 @@
 from . import tl
 from . import mag
 
-# Let users know if they're missing any of our hard dependencies
-HARD_DEPENDENCIES = ("numpy", "pandas", "scipy", "shapely")
-MISSING_DEPENDENCIES = []
-
-for dependency in HARD_DEPENDENCIES:
-    try:
-        __import__(dependency)
-    except ImportError:
-        MISSING_DEPENDENCIES.append(dependency)
-
-if MISSING_DEPENDENCIES:
-    raise ImportError(
-        "Missing required dependencies {0}".format(MISSING_DEPENDENCIES))
-del HARD_DEPENDENCIES, MISSING_DEPENDENCIES, dependency
+__version__ = '0.1.0'

bezpy/mt/__init__.py

@@ -3,4 +3,3 @@
 from .impulse import *
 from .utils import *
 from .io import *
-from .plotting import *

bezpy/mt/site.py

@@ -7,10 +7,8 @@
 import numpy as np
 import pandas as pd
 import scipy.interpolate
-import matplotlib.pyplot as plt
 
 from .utils import apparent_resistivity
-from .plotting import plot_apparent_resistivity
 
 # ----------------------------
 # Constants
@@ -184,6 +182,8 @@ def spline_interp(self, freqs, logspace=True, extrapolate=1,
 
     def plot_apparent_resistivity(self, interp_freqs=None):
         """Plot the apparent resistivity and phase of the transfer function."""
+        # lazy-load this so we don't require matplotlib to be installed by default
+        from .plotting import plot_apparent_resistivity
         xlim = [10**np.floor(np.log10(np.min(self.periods))),
                 10**np.ceil(np.log10(np.max(self.periods)))]
         fig, ax_res, ax_phase = plot_apparent_resistivity(self.periods, self.Z, self.Z_var,
@@ -262,6 +262,8 @@ def _repr_html_(self):
 
     def plot_depth(self, ax=None):
         """Plots the resistivity vs. depth profile."""
+        # lazy-load this so we don't require matplotlib to be installed by default
+        import matplotlib.pyplot as plt
         if ax is None:
             _, ax = plt.subplots()
         ax.step(self.resistivities, np.insert(self.depths, 0, 0)/1000., label=self.name)
@@ -313,6 +315,8 @@ def calcZ(self, freqs):
 
     def plot_apparent_resistivity(self, interp_freqs=None):
         """Plots the apparent resistivity and phase for the site."""
+        # lazy-load this so we don't require matplotlib to be installed by default
+        from .plotting import plot_apparent_resistivity
         if interp_freqs is None:
             raise ValueError("Need interpolation frequencies to plot the resistivity at.")