Implement get_value, so analysis branch and this branch can be merged…

… to master

src/graspfile/grid.py

@@ -1,8 +1,12 @@
 """This is the module for manipulating grid files containing one or more field cuts from TICRA Tools, GRASP and CHAMP
 """
 
-import configparser
+try:
+    import configparser
+except ImportError:
+    import ConfigParser as configparser
 
+import graspfile.numpy_utilities as numpy_utilities
 import numpy
 
 
@@ -134,6 +138,21 @@ def positions_1d(self):
         return (numpy.linspace(self.grid_min_x, self.grid_max_x, self.grid_n_x),
                 numpy.linspace(self.grid_min_y, self.grid_max_y, self.grid_n_y))
 
+    def get_value(self, xv, yv):
+        """Return the value of the field at the nearest point to xv, yv
+
+        Args:
+            xv: float containing the x coordinate of the point to get.
+            yv: float containing the y coordinate of the point to get.
+        Returns:
+            ndarray: containing self.field_components values of the field at xv, yv"""
+        x_vals, y_vals = self.positions_1d
+
+        nx = numpy_utilities.find_nearest_idx(x_vals, xv)
+        ny = numpy_utilities.find_nearest_idx(y_vals, yv)
+
+        return self.field[nx, ny, :]
+
     def radius_grid(self, center=None):
         """Return an array holding the radii of each point from the beam centre.
 

tests/test_analysis_grid.py

@@ -35,6 +35,27 @@ def filled_grasp_field(filled_grasp_grid):
     return filled_grasp_grid.fields[0]
 
 
+def test_get_value(filled_grasp_field):
+    """Test getting a value from the field"""
+    x_vals, y_vals = filled_grasp_field.positions_1d
+
+    # Test values of xv, yv in x_vals, y_vals
+    xv = x_vals[int(len(x_vals)/3)]
+    yv = y_vals[int(2*len(y_vals)/3)]
+
+    value = filled_grasp_field.get_value(xv, yv)
+
+    assert len(value) == filled_grasp_field.field_components
+
+    # Test values of xv, yv not in x_vals, y_vals
+    xv = (x_vals[int(len(x_vals)/3)] + x_vals[int(len(x_vals)/3)+1])/2
+    yv = (y_vals[int(2*len(y_vals)/3)] + y_vals[int(2*len(y_vals)/3)-1])/2
+
+    value = filled_grasp_field.get_value(xv, yv)
+
+    assert len(value) == filled_grasp_field.field_components
+
+
 def test_finding_peak(filled_grasp_field):
     """Test find the peak of a grasp field"""
     x_peak, y_peak = ga.find_peak(filled_grasp_field)