Merge pull request #12388 from mhvk/linspace-allow-array

ENH: allow arrays for start and stop in {lin,log,geom}space

1 files changed, 80 insertions, 38 deletions

diff --git a/numpy/core/function_base.py b/numpy/core/function_base.py
index 0fc56e70e..b68fd4068 100644
--- a/numpy/core/function_base.py
+++ b/numpy/core/function_base.py
@@ -29,13 +29,14 @@ def _index_deprecate(i, stacklevel=2):
     return i
 
 
-def _linspace_dispatcher(
-        start, stop, num=None, endpoint=None, retstep=None, dtype=None):
+def _linspace_dispatcher(start, stop, num=None, endpoint=None, retstep=None,
+                         dtype=None, axis=None):
     return (start, stop)
 
 
 @array_function_dispatch(_linspace_dispatcher)
-def linspace(start, stop, num=50, endpoint=True, retstep=False, dtype=None):
+def linspace(start, stop, num=50, endpoint=True, retstep=False, dtype=None,
+             axis=0):
     """
     Return evenly spaced numbers over a specified interval.
 
@@ -44,11 +45,14 @@ def linspace(start, stop, num=50, endpoint=True, retstep=False, dtype=None):
 
     The endpoint of the interval can optionally be excluded.
 
+    .. versionchanged:: 1.16.0
+        Non-scalar `start` and `stop` are now supported.
+
     Parameters
     ----------
-    start : scalar
+    start : array_like
         The starting value of the sequence.
-    stop : scalar
+    stop : array_like
         The end value of the sequence, unless `endpoint` is set to False.
         In that case, the sequence consists of all but the last of ``num + 1``
         evenly spaced samples, so that `stop` is excluded.  Note that the step
@@ -67,6 +71,13 @@ def linspace(start, stop, num=50, endpoint=True, retstep=False, dtype=None):
 
         .. versionadded:: 1.9.0
 
+    axis : int, optional
+        The axis in the result to store the samples.  Relevant only if start
+        or stop are array-like.  By default (0), the samples will be along a
+        new axis inserted at the beginning. Use -1 to get an axis at the end.
+
+        .. versionadded:: 1.16.0
+
     Returns
     -------
     samples : ndarray
@@ -128,16 +139,15 @@ def linspace(start, stop, num=50, endpoint=True, retstep=False, dtype=None):
     if dtype is None:
         dtype = dt
 
-    y = _nx.arange(0, num, dtype=dt)
-
     delta = stop - start
+    y = _nx.arange(0, num, dtype=dt).reshape((-1,) + (1,) * delta.ndim)
     # In-place multiplication y *= delta/div is faster, but prevents the multiplicant
     # from overriding what class is produced, and thus prevents, e.g. use of Quantities,
     # see gh-7142. Hence, we multiply in place only for standard scalar types.
-    _mult_inplace = _nx.isscalar(delta) 
+    _mult_inplace = _nx.isscalar(delta)
     if num > 1:
         step = delta / div
-        if step == 0:
+        if _nx.any(step == 0):
             # Special handling for denormal numbers, gh-5437
             y /= div
             if _mult_inplace:
@@ -160,19 +170,23 @@ def linspace(start, stop, num=50, endpoint=True, retstep=False, dtype=None):
     if endpoint and num > 1:
         y[-1] = stop
 
+    if axis != 0:
+        y = _nx.moveaxis(y, 0, axis)
+
     if retstep:
         return y.astype(dtype, copy=False), step
     else:
         return y.astype(dtype, copy=False)
 
 
-def _logspace_dispatcher(
-        start, stop, num=None, endpoint=None, base=None, dtype=None):
+def _logspace_dispatcher(start, stop, num=None, endpoint=None, base=None,
+                         dtype=None, axis=None):
     return (start, stop)
 
 
 @array_function_dispatch(_logspace_dispatcher)
-def logspace(start, stop, num=50, endpoint=True, base=10.0, dtype=None):
+def logspace(start, stop, num=50, endpoint=True, base=10.0, dtype=None,
+             axis=0):
     """
     Return numbers spaced evenly on a log scale.
 
@@ -180,11 +194,14 @@ def logspace(start, stop, num=50, endpoint=True, base=10.0, dtype=None):
     (`base` to the power of `start`) and ends with ``base ** stop``
     (see `endpoint` below).
 
+    .. versionchanged:: 1.16.0
+        Non-scalar `start` and `stop` are now supported.
+
     Parameters
     ----------
-    start : float
+    start : array_like
         ``base ** start`` is the starting value of the sequence.
-    stop : float
+    stop : array_like
         ``base ** stop`` is the final value of the sequence, unless `endpoint`
         is False.  In that case, ``num + 1`` values are spaced over the
         interval in log-space, of which all but the last (a sequence of
@@ -201,6 +218,13 @@ def logspace(start, stop, num=50, endpoint=True, base=10.0, dtype=None):
     dtype : dtype
         The type of the output array.  If `dtype` is not given, infer the data
         type from the other input arguments.
+    axis : int, optional
+        The axis in the result to store the samples.  Relevant only if start
+        or stop are array-like.  By default (0), the samples will be along a
+        new axis inserted at the beginning. Use -1 to get an axis at the end.
+
+        .. versionadded:: 1.16.0
+
 
     Returns
     -------
@@ -250,29 +274,33 @@ def logspace(start, stop, num=50, endpoint=True, base=10.0, dtype=None):
     >>> plt.show()
 
     """
-    y = linspace(start, stop, num=num, endpoint=endpoint)
+    y = linspace(start, stop, num=num, endpoint=endpoint, axis=axis)
     if dtype is None:
         return _nx.power(base, y)
-    return _nx.power(base, y).astype(dtype)
+    return _nx.power(base, y).astype(dtype, copy=False)
 
 
-def _geomspace_dispatcher(start, stop, num=None, endpoint=None, dtype=None):
+def _geomspace_dispatcher(start, stop, num=None, endpoint=None, dtype=None,
+                          axis=None):
     return (start, stop)
 
 
 @array_function_dispatch(_geomspace_dispatcher)
-def geomspace(start, stop, num=50, endpoint=True, dtype=None):
+def geomspace(start, stop, num=50, endpoint=True, dtype=None, axis=0):
     """
     Return numbers spaced evenly on a log scale (a geometric progression).
 
     This is similar to `logspace`, but with endpoints specified directly.
     Each output sample is a constant multiple of the previous.
 
+    .. versionchanged:: 1.16.0
+        Non-scalar `start` and `stop` are now supported.
+
     Parameters
     ----------
-    start : scalar
+    start : array_like
         The starting value of the sequence.
-    stop : scalar
+    stop : array_like
         The final value of the sequence, unless `endpoint` is False.
         In that case, ``num + 1`` values are spaced over the
         interval in log-space, of which all but the last (a sequence of
@@ -285,6 +313,12 @@ def geomspace(start, stop, num=50, endpoint=True, dtype=None):
     dtype : dtype
         The type of the output array.  If `dtype` is not given, infer the data
         type from the other input arguments.
+    axis : int, optional
+        The axis in the result to store the samples.  Relevant only if start
+        or stop are array-like.  By default (0), the samples will be along a
+        new axis inserted at the beginning. Use -1 to get an axis at the end.
+
+        .. versionadded:: 1.16.0
 
     Returns
     -------
@@ -349,40 +383,48 @@ def geomspace(start, stop, num=50, endpoint=True, dtype=None):
     >>> plt.show()
 
     """
-    if start == 0 or stop == 0:
+    start = asanyarray(start)
+    stop = asanyarray(stop)
+    if _nx.any(start == 0) or _nx.any(stop == 0):
         raise ValueError('Geometric sequence cannot include zero')
 
-    dt = result_type(start, stop, float(num))
+    dt = result_type(start, stop, float(num), _nx.zeros((), dtype))
     if dtype is None:
         dtype = dt
     else:
         # complex to dtype('complex128'), for instance
         dtype = _nx.dtype(dtype)
 
+    # Promote both arguments to the same dtype in case, for instance, one is
+    # complex and another is negative and log would produce NaN otherwise.
+    # Copy since we may change things in-place further down.
+    start = start.astype(dt, copy=True)
+    stop = stop.astype(dt, copy=True)
+
+    out_sign = _nx.ones(_nx.broadcast(start, stop).shape, dt)
     # Avoid negligible real or imaginary parts in output by rotating to
     # positive real, calculating, then undoing rotation
-    out_sign = 1
-    if start.real == stop.real == 0:
-        start, stop = start.imag, stop.imag
-        out_sign = 1j * out_sign
-    if _nx.sign(start) == _nx.sign(stop) == -1:
-        start, stop = -start, -stop
-        out_sign = -out_sign
-
-    # Promote both arguments to the same dtype in case, for instance, one is
-    # complex and another is negative and log would produce NaN otherwise
-    start = start + (stop - stop)
-    stop = stop + (start - start)
-    if _nx.issubdtype(dtype, _nx.complexfloating):
-        start = start + 0j
-        stop = stop + 0j
+    if _nx.issubdtype(dt, _nx.complexfloating):
+        all_imag = (start.real == 0.) & (stop.real == 0.)
+        if _nx.any(all_imag):
+            start[all_imag] = start[all_imag].imag
+            stop[all_imag] = stop[all_imag].imag
+            out_sign[all_imag] = 1j
+
+    both_negative = (_nx.sign(start) == -1) & (_nx.sign(stop) == -1)
+    if _nx.any(both_negative):
+        _nx.negative(start, out=start, where=both_negative)
+        _nx.negative(stop, out=stop, where=both_negative)
+        _nx.negative(out_sign, out=out_sign, where=both_negative)
 
     log_start = _nx.log10(start)
     log_stop = _nx.log10(stop)
     result = out_sign * logspace(log_start, log_stop, num=num,
                                  endpoint=endpoint, base=10.0, dtype=dtype)
+    if axis != 0:
+        result = _nx.moveaxis(result, 0, axis)
 
-    return result.astype(dtype)
+    return result.astype(dtype, copy=False)
 
 
 #always succeed