ENH: Add pandas_compat.table_from_frame(df)

.travis/install_orange.sh

@@ -7,6 +7,7 @@ foldable pip install -U setuptools pip codecov
 cat requirements-core.txt \
     requirements-gui.txt \
     requirements-dev.txt \
+    requirements-opt.txt \
     requirements-doc.txt |
     while read dep; do
         dep="${dep%%#*}"  # Strip the comment

Orange/data/pandas_compat.py

@@ -0,0 +1,78 @@
+"""Pandas DataFrame↔Table conversion helpers"""
+import numpy as np
+import pandas as pd
+from pandas.api.types import (
+    is_categorical_dtype, is_object_dtype,
+    is_datetime64_any_dtype, is_numeric_dtype,
+)
+
+from Orange.data import (
+    Table, Domain, DiscreteVariable, StringVariable, TimeVariable,
+    ContinuousVariable,
+)
+
+__all__ = ['table_from_frame']
+
+
+def table_from_frame(df, *, force_nominal=False):
+    """
+    Convert pandas.DataFrame to Orange.data.Table
+
+    Parameters
+    ----------
+    df : pandas.DataFrame
+    force_nominal : boolean
+        If True, interpret ALL string columns as nominal (DiscreteVariable).
+
+    Returns
+    -------
+    Table
+    """
+
+    def _is_discrete(s):
+        return (is_categorical_dtype(s) or
+                is_object_dtype(s) and (force_nominal or
+                                        s.nunique() < s.size**.666))
+
+    def _is_datetime(s):
+        if is_datetime64_any_dtype(s):
+            return True
+        try:
+            if is_object_dtype(s):
+                pd.to_datetime(s, infer_datetime_format=True)
+                return True
+        except Exception:  # pylint: disable=broad-except
+            pass
+        return False
+
+    # If df index is not a simple RangeIndex (or similar), put it into data
+    if not (df.index.is_integer() and (df.index.is_monotonic_increasing or
+                                       df.index.is_monotonic_decreasing)):
+        df = df.reset_index()
+
+    attrs, metas = [], []
+    X, M = [], []
+
+    # Iter over columns
+    for name, s in df.items():
+        name = str(name)
+        if _is_discrete(s):
+            discrete = s.astype('category').cat
+            attrs.append(DiscreteVariable(name, discrete.categories.astype(str).tolist()))
+            X.append(discrete.codes.replace(-1, np.nan).values)
+        elif _is_datetime(s):
+            tvar = TimeVariable(name)
+            attrs.append(tvar)
+            s = pd.to_datetime(s, infer_datetime_format=True)
+            X.append(s.astype('str').replace('NaT', np.nan).map(tvar.parse).values)
+        elif is_numeric_dtype(s):
+            attrs.append(ContinuousVariable(name))
+            X.append(s.values)
+        else:
+            metas.append(StringVariable(name))
+            M.append(s.values.astype(object))
+
+    return Table.from_numpy(Domain(attrs, None, metas),
+                            np.column_stack(X) if X else np.empty((df.shape[0], 0)),
+                            None,
+                            np.column_stack(M) if M else None)

Orange/data/tests/test_pandas.py

@@ -0,0 +1,62 @@
+import unittest
+import numpy as np
+from Orange.data import ContinuousVariable, DiscreteVariable, TimeVariable
+
+try:
+    import pandas as pd
+except ImportError:
+    pd = None
+
+@unittest.skipIf(pd is None, "Missing package 'pandas'")
+class TestPandasCompat(unittest.TestCase):
+    def test_table_from_frame(self):
+        from Orange.data.pandas_compat import table_from_frame
+
+        nan = np.nan
+        df = pd.DataFrame([['a', 1, pd.Timestamp('2017-12-19')],
+                           ['b', 0, pd.Timestamp('1724-12-20')],
+                           ['c', 0, pd.Timestamp('1724-12-20')],
+                           [nan, nan, nan]])
+        table = table_from_frame(df)
+        np.testing.assert_equal(table.X,
+                                [[1, pd.Timestamp('2017-12-19').timestamp()],
+                                 [0, pd.Timestamp('1724-12-20').timestamp()],
+                                 [0, pd.Timestamp('1724-12-20').timestamp()],
+                                 [nan, nan]])
+        np.testing.assert_equal(table.metas.tolist(), [['a'],
+                                                       ['b'],
+                                                       ['c'],
+                                                       [nan]])
+        names = [var.name for var in table.domain.attributes]
+        types = [type(var) for var in table.domain.attributes]
+        self.assertEqual(names, ['1', '2'])
+        self.assertEqual(types, [ContinuousVariable, TimeVariable])
+
+        # Force strings nominal
+        table = table_from_frame(df, force_nominal=True)
+        np.testing.assert_equal(table.X, [[0, 1, pd.Timestamp('2017-12-19').timestamp()],
+                                          [1, 0, pd.Timestamp('1724-12-20').timestamp()],
+                                          [2, 0, pd.Timestamp('1724-12-20').timestamp()],
+                                          [nan, nan, nan]])
+        np.testing.assert_equal(table.metas.tolist(), [[], [], [], []])
+        names = [var.name for var in table.domain.attributes]
+        types = [type(var) for var in table.domain.attributes]
+        self.assertEqual(names, ['0', '1', '2'])
+        self.assertEqual(types, [DiscreteVariable, ContinuousVariable, TimeVariable])
+
+        # Include index
+        df.index = list('abaa')
+        table = table_from_frame(df)
+        np.testing.assert_equal(table.X,
+                                [[0, 1, pd.Timestamp('2017-12-19').timestamp()],
+                                 [1, 0, pd.Timestamp('1724-12-20').timestamp()],
+                                 [0, 0, pd.Timestamp('1724-12-20').timestamp()],
+                                 [0, nan, nan]])
+        np.testing.assert_equal(table.metas.tolist(), [['a'],
+                                                       ['b'],
+                                                       ['c'],
+                                                       [nan]])
+        names = [var.name for var in table.domain.attributes]
+        types = [type(var) for var in table.domain.attributes]
+        self.assertEqual(names, ['index', '1', '2'])
+        self.assertEqual(types, [DiscreteVariable, ContinuousVariable, TimeVariable])

appveyor.yml

@@ -21,7 +21,7 @@ environment:
     BUILD_GLOBAL_OPTIONS: build -j1
     BUILD_ENV: wheel==0.29.0 pip==9.0.1 numpy==1.9.3
     # SIP 4.19.4+ with PyQt5==5.9.1+ segfault our tests (GH-2756)
-    TEST_ENV: sip==4.19.6 PyQt5==5.9.2 numpy==1.12.1 scipy==1.0.0b1 scikit-learn
+    TEST_ENV: sip==4.19.6 PyQt5==5.9.2 numpy==1.12.1 scipy==1.0.0b1 scikit-learn pandas==0.21.1
 
   matrix:
     - PYTHON: C:\Python34

requirements-opt.txt

@@ -1,5 +1 @@
-# This is required for, and only used by, Parallel Coordinates widget.
-# Once that is ported to whatever, this can be removed, along with
-# Orange/widgets/utils/plot/*
-# Optional because it's hard to install everywhere.
-qt-graph-helpers>=0.1.3
+pandas