Add function for selection of value closer to comparative value

Author: SabineHaas

windpowerlib/tools.py

@@ -6,3 +6,66 @@
 
 __copyright__ = "Copyright oemof developer group"
 __license__ = "GPLv3"
+
+import collections
+
+
+def select_closer_value(value_1, value_2, comp_value, corresp_1, corresp_2):
+    r"""
+    Selects the value with the smaller difference to a comparative value.
+
+    Additionally returns a corresponding value. This function is for example
+    used in :py:func:`~.modelchain.v_wind_hub` of the
+    :class:`~.modelchain.ModelChain` to choose the wind speed data that is
+    close to the hub height of the examined wind turbine. In this case
+    `value_1` and `value_2` are the heights of the corresponding wind speed
+    data sets `corresp_1` and `corresp_2`.
+
+    Parameters
+    ----------
+    value_1 : float
+        First value of which the difference to `comp_value` will be
+        compared with the difference to `comp_value` of `value_2`.
+    value_2 : float
+        Second value for comparison.
+    comp_value : float
+        Comparative value.
+    corresp_1 : float
+        Corresponding value to `value_1`.
+    corresp_2 : float
+        Corresponding value to `value_2`.
+
+    Returns
+    -------
+    Tuple(float, float, string)
+        Value closer to comparing value as float, corresponding value as
+        float and a string for logging.debug.
+    """
+    if (value_2 is not None and corresp_2 is not None):
+        if value_1 == comp_value:
+            closest_value = value_1
+            logging_string = '(at hub height).'
+        elif value_2 == comp_value:
+            closest_value = value_2
+            logging_string = '(2) (at hub height).'
+        elif abs(value_1 - comp_value) <= abs(value_2 - comp_value):
+            closest_value = value_1
+            logging_string = None
+        else:
+            closest_value = value_2
+            logging_string = None
+    else:
+        closest_value = value_1
+        if value_1 == comp_value:
+            logging_string = '(at hub height).'
+
+    # Select correponding value
+    if closest_value == value_1:
+        corresp_value = corresp_1
+    else:
+        corresp_value = corresp_2
+    # Store values in a named tuple
+    return_tuple = collections.namedtuple('selected_values',
+                                          ['closest_value',
+                                           'corresp_value', 'logging_string'])
+    return return_tuple(closest_value, corresp_value, logging_string)