Concat neq dfs0

mikeio/generic.py

@@ -27,6 +27,7 @@
 from . import __dfs_version__
 from .dfs._dfs import _get_item_info, _valid_item_numbers
 from .eum import ItemInfo
+import mikeio
 
 
 TimeAxis = Union[
@@ -449,6 +450,13 @@ def concat(
 
     The list of input files have to be sorted, i.e. in chronological order
     """
+    # fast path for Dfs0
+    suffix = pathlib.Path(infilenames[0]).suffix
+    if suffix == ".dfs0":
+        dss = [mikeio.read(f) for f in infilenames]
+        ds = mikeio.Dataset.concat(dss, keep=keep)  # type: ignore
+        ds.to_dfs(outfilename)
+        return
 
     dfs_i_a = DfsFileFactory.DfsGenericOpen(str(infilenames[0]))
 

tests/test_generic.py

@@ -318,6 +318,39 @@ def test_concat_keep(tmp_path):
                     assert last_out, "overlap should be with last dataset"
 
 
+def test_concat_non_equidistant_dfs0(tmp_path):
+
+    # create two non-equidistant dfs0 files
+    da1 = mikeio.DataArray(
+        data=np.array([0.0, 0.1, 0.2]),
+        time=pd.DatetimeIndex(
+            ["2017-10-27 01:58", "2017-10-27 04:32", "2017-10-27 05:32"]
+        ),
+    )
+    assert not da1.is_equidistant
+    da2 = mikeio.DataArray(
+        data=np.array([0.9, 1.1, 0.2]),
+        time=pd.DatetimeIndex(
+            ["2017-10-28 01:59", "2017-10-29 04:32", "2017-11-01 05:32"]
+        ),
+    )
+    assert not da2.is_equidistant
+    files = [tmp_path / "da1.dfs0", tmp_path / "da2.dfs0"]
+    da1.to_dfs(tmp_path / "da1.dfs0")
+    da2.to_dfs(tmp_path / "da2.dfs0")
+
+    # concatenate
+    fp = tmp_path / "concat.dfs0"
+    mikeio.generic.concat(files, fp)
+
+    ds = mikeio.read(fp)
+    assert len(ds.time) == 6
+
+    assert ds.sel(time="2017-10-29 04:32").to_dataframe().iloc[0, 0] == pytest.approx(
+        1.1
+    )
+
+
 def test_extract_equidistant(tmp_path):
 
     infile = "tests/testdata/waves.dfs2"