Fix matplotlib errors

pybamm/plotting/plot.py

@@ -3,6 +3,7 @@
 #
 import pybamm
 from .quick_plot import ax_min, ax_max
+from pybamm.util import have_optional_dependency
 
 
 def plot(x, y, ax=None, testing=False, **kwargs):
@@ -25,7 +26,7 @@ def plot(x, y, ax=None, testing=False, **kwargs):
         Keyword arguments, passed to plt.plot
 
     """
-    import matplotlib.pyplot as plt
+    plt = have_optional_dependency("matplotlib.pyplot")
 
     if not isinstance(x, pybamm.Array):
         raise TypeError("x must be 'pybamm.Array'")

pybamm/plotting/plot2D.py

@@ -3,6 +3,7 @@
 #
 import pybamm
 from .quick_plot import ax_min, ax_max
+from pybamm.util import have_optional_dependency
 
 
 def plot2D(x, y, z, ax=None, testing=False, **kwargs):
@@ -25,7 +26,7 @@ def plot2D(x, y, z, ax=None, testing=False, **kwargs):
         Whether to actually make the plot (turned off for unit tests)
 
     """
-    import matplotlib.pyplot as plt
+    plt = have_optional_dependency("matplotlib.pyplot")
 
     if not isinstance(x, pybamm.Array):
         raise TypeError("x must be 'pybamm.Array'")

pybamm/plotting/plot_summary_variables.py

@@ -3,6 +3,7 @@
 #
 import numpy as np
 import pybamm
+from pybamm.util import have_optional_dependency
 
 
 def plot_summary_variables(
@@ -25,7 +26,7 @@ def plot_summary_variables(
         Keyword arguments, passed to plt.subplots.
 
     """
-    import matplotlib.pyplot as plt
+    plt = have_optional_dependency("matplotlib.pyplot")
 
     if isinstance(solutions, pybamm.Solution):
         solutions = [solutions]

pybamm/plotting/plot_voltage_components.py

@@ -3,6 +3,8 @@
 #
 import numpy as np
 
+from pybamm.util import have_optional_dependency
+
 
 def plot_voltage_components(
     solution,
@@ -32,7 +34,7 @@ def plot_voltage_components(
         Keyword arguments, passed to ax.fill_between
 
     """
-    import matplotlib.pyplot as plt
+    plt = have_optional_dependency("matplotlib.pyplot")
 
     # Set a default value for alpha, the opacity
     kwargs_fill = {"alpha": 0.6, **kwargs_fill}

pybamm/plotting/quick_plot.py

@@ -5,6 +5,7 @@
 import numpy as np
 import pybamm
 from collections import defaultdict
+from pybamm.util import have_optional_dependency
 
 
 class LoopList(list):
@@ -46,7 +47,7 @@ def split_long_string(title, max_words=None):
 
 def close_plots():
     """Close all open figures"""
-    import matplotlib.pyplot as plt
+    plt = have_optional_dependency("matplotlib", "pyplot")
 
     plt.close("all")
 
@@ -469,9 +470,10 @@ def plot(self, t, dynamic=False):
             Dimensional time (in 'time_units') at which to plot.
         """
 
-        import matplotlib.pyplot as plt
-        import matplotlib.gridspec as gridspec
-        from matplotlib import cm, colors
+        plt = have_optional_dependency("matplotlib.pyplot")
+        gridspec = have_optional_dependency("matplotlib.gridspec")
+        cm = have_optional_dependency("matplotlib", "cm")
+        colors = have_optional_dependency("matplotlib", "colors")
 
         t_in_seconds = t * self.time_scaling_factor
         self.fig = plt.figure(figsize=self.figsize)
@@ -668,8 +670,8 @@ def dynamic_plot(self, testing=False, step=None):
                 continuous_update=False,
             )
         else:
-            import matplotlib.pyplot as plt
-            from matplotlib.widgets import Slider
+            plt = have_optional_dependency("matplotlib.pyplot")
+            Slider = have_optional_dependency("matplotlib.widgets", "Slider")
 
             # create an initial plot at time self.min_t
             self.plot(self.min_t, dynamic=True)
@@ -773,8 +775,8 @@ def create_gif(self, number_of_images=80, duration=0.1, output_filename="plot.gi
             Name of the generated GIF file.
 
         """
-        import imageio.v2 as imageio
-        import matplotlib.pyplot as plt
+        imageio = have_optional_dependency("imageio.v2")
+        plt = have_optional_dependency("matplotlib.pyplot")
 
         # time stamps at which the images/plots will be created
         time_array = np.linspace(self.min_t, self.max_t, num=number_of_images)