Allow modification of unit

mikeio/dataset/_dataarray.py

@@ -407,7 +407,11 @@ def type(self) -> EUMType:
     @property
     def unit(self) -> EUMUnit:
         """EUMUnit."""
-        return self.item.unit
+        return self.item._unit
+
+    @unit.setter
+    def unit(self, value: EUMUnit) -> None:
+        self.item.unit = value
 
     @property
     def start_time(self) -> datetime:

mikeio/eum/_eum.py

@@ -1465,12 +1465,12 @@ def __init__(
                 raise ValueError(
                     "Invalid unit. Unit should be supplied as EUMUnit, e.g. ItemInfo('WL',EUMType.Water_Level, EUMUnit.meter)"
                 )
-            self.unit = unit
+            self._unit = unit
         else:
             if self.type == EUMType.Undefined:
-                self.unit = EUMUnit.undefined
+                self._unit = EUMUnit.undefined
             else:
-                self.unit = self.type.units[0]
+                self._unit = self.type.units[0]
 
         self.data_value_type = to_datatype(data_value_type)
 
@@ -1496,6 +1496,20 @@ def __repr__(self) -> str:
         else:
             return f"{self.name} <{self.type.display_name}> ({self.unit.display_name}) - {self.data_value_type}"
 
+    @property
+    def unit(self) -> EUMUnit:
+        "Item unit."
+        return self._unit
+
+    @unit.setter
+    def unit(self, value: EUMUnit) -> None:
+        "Set unit."
+        if value not in self.type.units:
+            raise ValueError(
+                f"{value} is not a correct unit for {self.type}. Use {self.type.units}"
+            )
+        self._unit = value
+
     @staticmethod
     def from_mikecore_dynamic_item_info(dfsItemInfo: DfsDynamicItemInfo) -> "ItemInfo":
         """Create ItemInfo from a mikecore.DfsDynamicItemInfo object."""

tests/test_dataarray.py

@@ -1376,3 +1376,24 @@ def test_set_by_mask():
     mask = da < threshold
     wl_capped = da.copy()
     wl_capped[mask] = np.nan
+
+
+def test_set_unit() -> None:
+    da = mikeio.DataArray(
+        data=np.array([0.0, 1.0]),
+        item=mikeio.ItemInfo("Water", mikeio.EUMType.Water_Level, mikeio.EUMUnit.meter),
+    )
+
+    da.unit = mikeio.EUMUnit.feet
+
+    assert da.unit == mikeio.EUMUnit.feet
+
+
+def test_set_bad_unit_fails() -> None:
+    da = mikeio.DataArray(
+        data=np.array([0.0, 1.0]),
+        item=mikeio.ItemInfo("Water", mikeio.EUMType.Water_Level, mikeio.EUMUnit.meter),
+    )
+
+    with pytest.raises(ValueError, match="unit"):
+        da.unit = mikeio.EUMUnit.decibar