RF - reverse arg order for arraywriter factory

The order was has_intercept, has_slope, because the default for both was
true, and it is more common to not want an intercept, than not want a
slope.

However, (slope, inter) are elsewhere in that order (for example in the
class names and in ``get_slope_inter``). I changed the argument order to
fit that convention.

Author: matthew-brett

nibabel/analyze.py

@@ -528,8 +528,8 @@ def data_to_fileobj(self, data, fileobj):
         try:
             arr_writer = make_array_writer(data,
                                            out_dtype,
-                                           self.has_data_intercept,
-                                           self.has_data_slope)
+                                           self.has_data_slope,
+                                           self.has_data_intercept)
         except WriterError:
             msg = sys.exc_info()[1] # python 2 / 3 compatibility
             raise HeaderTypeError(msg)
@@ -934,8 +934,8 @@ def to_file_map(self, file_map=None):
         out_dtype = self.get_data_dtype()
         arr_writer = make_array_writer(data,
                                        out_dtype,
-                                       hdr.has_data_intercept,
-                                       hdr.has_data_slope)
+                                       hdr.has_data_slope,
+                                       hdr.has_data_intercept)
         hdr_fh, img_fh = self._get_fileholders(file_map)
         # Check if hdr and img refer to same file; this can happen with odd
         # analyze images but most often this is because it's a single nifti file

nibabel/arraywriters.py

@@ -534,7 +534,7 @@ def get_slope_inter(writer):
     return slope, inter
 
 
-def make_array_writer(data, out_type, has_intercept=True, has_slope=True,
+def make_array_writer(data, out_type, has_slope=True, has_intercept=True,
                       **kwargs):
     """ Make array writer instance for array `data` and output type `out_type`
 
@@ -544,10 +544,10 @@ def make_array_writer(data, out_type, has_intercept=True, has_slope=True,
         array for which to create array writer
     out_type : dtype-like
         input to numpy dtype to specify array writer output type
-    has_intercept : {True, False}
-        If True, array write can use intercept to adapt the array to `out_type`
     has_slope : {True, False}
         If True, array write can use scaling to adapt the array to `out_type`
+    has_intercept : {True, False}
+        If True, array write can use intercept to adapt the array to `out_type`
     \*\*kwargs : other keyword arguments
         to pass to the arraywriter class, if it accepts them.
 
@@ -562,7 +562,7 @@ def make_array_writer(data, out_type, has_intercept=True, has_slope=True,
     >>> aw = make_array_writer(np.arange(10), np.uint8, True, True)
     >>> type(aw) == SlopeInterArrayWriter
     True
-    >>> aw = make_array_writer(np.arange(10), np.uint8, False, True)
+    >>> aw = make_array_writer(np.arange(10), np.uint8, True, False)
     >>> type(aw) == SlopeArrayWriter
     True
     >>> aw = make_array_writer(np.arange(10), np.uint8, False, False)

nibabel/tests/test_arraywriters.py

@@ -467,11 +467,14 @@ def test_writer_maker():
     arr = np.arange(10, dtype=np.float64)
     aw = make_array_writer(arr, np.float64)
     assert_true(isinstance(aw, SlopeInterArrayWriter))
-    aw = make_array_writer(arr, np.float64, False)
+    aw = make_array_writer(arr, np.float64, True, True)
+    assert_true(isinstance(aw, SlopeInterArrayWriter))
+    aw = make_array_writer(arr, np.float64, True, False)
     assert_true(isinstance(aw, SlopeArrayWriter))
     aw = make_array_writer(arr, np.float64, False, False)
     assert_true(isinstance(aw, ArrayWriter))
-    assert_raises(ValueError, make_array_writer, arr, np.float64, True, False)
+    assert_raises(ValueError, make_array_writer, arr, np.float64, False)
+    assert_raises(ValueError, make_array_writer, arr, np.float64, False, True)
     # Does calc_scale get run by default?
     aw = make_array_writer(arr, np.int16, calc_scale=False)
     assert_equal((aw.slope, aw.inter), (1, 0))

nibabel/volumeutils.py

@@ -424,7 +424,7 @@ def can_cast(in_type, out_type, has_intercept=False, has_slope=False):
         data = np.ones((1,), in_type)
     from .arraywriters import make_array_writer, WriterError
     try:
-        _ = make_array_writer(data, out_type, has_intercept, has_slope)
+        _ = make_array_writer(data, out_type, has_slope, has_intercept)
     except WriterError:
         return False
     return True
@@ -778,7 +778,7 @@ def calculate_scale(data, out_dtype, allow_intercept):
         return 1.0, 0.0, None, None
     from .arraywriters import make_array_writer, WriterError, get_slope_inter
     try:
-        writer = make_array_writer(data, out_dtype, allow_intercept, True)
+        writer = make_array_writer(data, out_dtype, True, allow_intercept)
     except WriterError:
         msg = sys.exc_info()[1] # python 2 / 3 compatibility
         raise ValueError(msg)