diff options
Diffstat (limited to 'numpy/lib/function_base.py')
| -rw-r--r-- | numpy/lib/function_base.py | 114 |
1 files changed, 80 insertions, 34 deletions
diff --git a/numpy/lib/function_base.py b/numpy/lib/function_base.py index d875a00ae..20e32a78d 100644 --- a/numpy/lib/function_base.py +++ b/numpy/lib/function_base.py @@ -33,7 +33,7 @@ from numpy.core.umath import _add_newdoc_ufunc as add_newdoc_ufunc import builtins # needed in this module for compatibility -from numpy.lib.histograms import histogram, histogramdd +from numpy.lib.histograms import histogram, histogramdd # noqa: F401 array_function_dispatch = functools.partial( @@ -268,6 +268,19 @@ def iterable(y): >>> np.iterable(2) False + Notes + ----- + In most cases, the results of ``np.iterable(obj)`` are consistent with + ``isinstance(obj, collections.abc.Iterable)``. One notable exception is + the treatment of 0-dimensional arrays:: + + >>> from collections.abc import Iterable + >>> a = np.array(1.0) # 0-dimensional numpy array + >>> isinstance(a, Iterable) + True + >>> np.iterable(a) + False + """ try: iter(y) @@ -657,11 +670,16 @@ def select(condlist, choicelist, default=0): Examples -------- - >>> x = np.arange(10) - >>> condlist = [x<3, x>5] + >>> x = np.arange(6) + >>> condlist = [x<3, x>3] >>> choicelist = [x, x**2] - >>> np.select(condlist, choicelist) - array([ 0, 1, 2, ..., 49, 64, 81]) + >>> np.select(condlist, choicelist, 42) + array([ 0, 1, 2, 42, 16, 25]) + + >>> condlist = [x<=4, x>3] + >>> choicelist = [x, x**2] + >>> np.select(condlist, choicelist, 55) + array([ 0, 1, 2, 3, 4, 25]) """ # Check the size of condlist and choicelist are the same, or abort. @@ -779,6 +797,17 @@ def copy(a, order='K', subok=False): >>> x[0] == z[0] False + Note that, np.copy clears previously set WRITEABLE=False flag. + + >>> a = np.array([1, 2, 3]) + >>> a.flags["WRITEABLE"] = False + >>> b = np.copy(a) + >>> b.flags["WRITEABLE"] + True + >>> b[0] = 3 + >>> b + array([3, 2, 3]) + Note that np.copy is a shallow copy and will not copy object elements within arrays. This is mainly important for arrays containing Python objects. The new array will contain the @@ -2804,9 +2833,9 @@ def blackman(M): """ if M < 1: - return array([]) + return array([], dtype=np.result_type(M, 0.0)) if M == 1: - return ones(1, float) + return ones(1, dtype=np.result_type(M, 0.0)) n = arange(1-M, M, 2) return 0.42 + 0.5*cos(pi*n/(M-1)) + 0.08*cos(2.0*pi*n/(M-1)) @@ -2913,9 +2942,9 @@ def bartlett(M): """ if M < 1: - return array([]) + return array([], dtype=np.result_type(M, 0.0)) if M == 1: - return ones(1, float) + return ones(1, dtype=np.result_type(M, 0.0)) n = arange(1-M, M, 2) return where(less_equal(n, 0), 1 + n/(M-1), 1 - n/(M-1)) @@ -3017,9 +3046,9 @@ def hanning(M): """ if M < 1: - return array([]) + return array([], dtype=np.result_type(M, 0.0)) if M == 1: - return ones(1, float) + return ones(1, dtype=np.result_type(M, 0.0)) n = arange(1-M, M, 2) return 0.5 + 0.5*cos(pi*n/(M-1)) @@ -3117,9 +3146,9 @@ def hamming(M): """ if M < 1: - return array([]) + return array([], dtype=np.result_type(M, 0.0)) if M == 1: - return ones(1, float) + return ones(1, dtype=np.result_type(M, 0.0)) n = arange(1-M, M, 2) return 0.54 + 0.46*cos(pi*n/(M-1)) @@ -3252,7 +3281,7 @@ def i0(x): Her Majesty's Stationery Office, 1962. .. [2] M. Abramowitz and I. A. Stegun, *Handbook of Mathematical Functions*, 10th printing, New York: Dover, 1964, pp. 379. - http://www.math.sfu.ca/~cbm/aands/page_379.htm + https://personal.math.ubc.ca/~cbm/aands/page_379.htm .. [3] https://metacpan.org/pod/distribution/Math-Cephes/lib/Math/Cephes.pod#i0:-Modified-Bessel-function-of-order-zero Examples @@ -3396,7 +3425,7 @@ def kaiser(M, beta): """ if M == 1: - return np.array([1.]) + return np.ones(1, dtype=np.result_type(M, 0.0)) n = arange(0, M) alpha = (M-1)/2.0 return i0(beta * sqrt(1-((n-alpha)/alpha)**2.0))/i0(float(beta)) @@ -3714,16 +3743,15 @@ def _median(a, axis=None, out=None, overwrite_input=False): indexer[axis] = slice(index-1, index+1) indexer = tuple(indexer) + # Use mean in both odd and even case to coerce data type, + # using out array if needed. + rout = mean(part[indexer], axis=axis, out=out) # Check if the array contains any nan's if np.issubdtype(a.dtype, np.inexact) and sz > 0: - # warn and return nans like mean would - rout = mean(part[indexer], axis=axis, out=out) - return np.lib.utils._median_nancheck(part, rout, axis, out) - else: - # if there are no nans - # Use mean in odd and even case to coerce data type - # and check, use out array. - return mean(part[indexer], axis=axis, out=out) + # If nans are possible, warn and replace by nans like mean would. + rout = np.lib.utils._median_nancheck(part, rout, axis) + + return rout def _percentile_dispatcher(a, q, axis=None, out=None, overwrite_input=None, @@ -4277,7 +4305,13 @@ def meshgrid(*xi, copy=True, sparse=False, indexing='xy'): .. versionadded:: 1.7.0 sparse : bool, optional - If True a sparse grid is returned in order to conserve memory. + If True the shape of the returned coordinate array for dimension *i* + is reduced from ``(N1, ..., Ni, ... Nn)`` to + ``(1, ..., 1, Ni, 1, ..., 1)``. These sparse coordinate grids are + intended to be use with :ref:`basics.broadcasting`. When all + coordinates are used in an expression, broadcasting still leads to a + fully-dimensonal result array. + Default is False. .. versionadded:: 1.7.0 @@ -4348,17 +4382,30 @@ def meshgrid(*xi, copy=True, sparse=False, indexing='xy'): array([[0.], [1.]]) - `meshgrid` is very useful to evaluate functions on a grid. + `meshgrid` is very useful to evaluate functions on a grid. If the + function depends on all coordinates, you can use the parameter + ``sparse=True`` to save memory and computation time. + + >>> x = np.linspace(-5, 5, 101) + >>> y = np.linspace(-5, 5, 101) + >>> # full coorindate arrays + >>> xx, yy = np.meshgrid(x, y) + >>> zz = np.sqrt(xx**2 + yy**2) + >>> xx.shape, yy.shape, zz.shape + ((101, 101), (101, 101), (101, 101)) + >>> # sparse coordinate arrays + >>> xs, ys = np.meshgrid(x, y, sparse=True) + >>> zs = np.sqrt(xs**2 + ys**2) + >>> xs.shape, ys.shape, zs.shape + ((1, 101), (101, 1), (101, 101)) + >>> np.array_equal(zz, zs) + True >>> import matplotlib.pyplot as plt - >>> x = np.arange(-5, 5, 0.1) - >>> y = np.arange(-5, 5, 0.1) - >>> xx, yy = np.meshgrid(x, y, sparse=True) - >>> z = np.sin(xx**2 + yy**2) / (xx**2 + yy**2) - >>> h = plt.contourf(x, y, z) + >>> h = plt.contourf(x, y, zs) >>> plt.axis('scaled') + >>> plt.colorbar() >>> plt.show() - """ ndim = len(xi) @@ -4711,9 +4758,8 @@ def insert(arr, obj, values, axis=None): if indices.size == 1: index = indices.item() if index < -N or index > N: - raise IndexError( - "index %i is out of bounds for axis %i with " - "size %i" % (obj, axis, N)) + raise IndexError(f"index {obj} is out of bounds for axis {axis} " + f"with size {N}") if (index < 0): index += N |