BUG: stats.zscore returns all NaN if given masked array with first element masked #19039
Description
Describe your issue.
passing a masked array to scipy.stats.zscore yields results that are all nan when the first element of the array is masked.
Reproducing Code Example
import numpy as np
from scipy.stats import zscore
rng = np.random.default_rng(seed=8675309) # tried with 3 different seeds
x = rng.standard_normal(10)
mask = np.zeros_like(x)
y = np.ma.masked_array(x, mask)
y.mask[1] = True
print(zscore(y))
# [-0.6327236439032247 -- -0.6005585026611974 0.03365730448338995
# -0.9428312016417735 1.775001047420241 1.189629067553608
# -0.5510199319620768 -1.2407231008627846 0.9695689615738183]
y.mask[1] = False
y.mask[0] = True # still happens if additional elements are masked besides element [0]
print(zscore(y))
# [nan nan nan nan nan nan nan nan nan nan]Error message
n/aSciPy/NumPy/Python version and system information
1.11.1 1.25.2 sys.version_info(major=3, minor=11, micro=4, releaselevel='final', serial=0)
Build Dependencies:
blas:
detection method: pkgconfig
found: true
include directory: /opt/mambaforge/envs/mwe/include
lib directory: /opt/mambaforge/envs/mwe/lib
name: blas
openblas configuration: unknown
pc file directory: /opt/mambaforge/envs/mwe/lib/pkgconfig
version: 3.9.0
lapack:
detection method: pkgconfig
found: true
include directory: /opt/mambaforge/envs/mwe/include
lib directory: /opt/mambaforge/envs/mwe/lib
name: lapack
openblas configuration: unknown
pc file directory: /opt/mambaforge/envs/mwe/lib/pkgconfig
version: 3.9.0
pybind11:
detection method: pkgconfig
include directory: /opt/mambaforge/envs/mwe/include
name: pybind11
version: 2.10.4
Compilers:
c:
commands: /home/conda/feedstock_root/build_artifacts/scipy-split_1687995550978/_build_env/bin/x86_64-conda-linux-gnu-cc
linker: ld.bfd
name: gcc
version: 12.3.0
c++:
commands: /home/conda/feedstock_root/build_artifacts/scipy-split_1687995550978/_build_env/bin/x86_64-conda-linux-gnu-c++
linker: ld.bfd
name: gcc
version: 12.3.0
cython:
commands: cython
linker: cython
name: cython
version: 0.29.35
fortran:
commands: /home/conda/feedstock_root/build_artifacts/scipy-split_1687995550978/_build_env/bin/x86_64-conda-linux-gnu-gfortran
linker: ld.bfd
name: gcc
version: 12.3.0
pythran:
include directory: ../../../_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold/lib/python3.11/site-packages/pythran
version: 0.13.1
Machine Information:
build:
cpu: x86_64
endian: little
family: x86_64
system: linux
cross-compiled: false
host:
cpu: x86_64
endian: little
family: x86_64
system: linux
Python Information:
path: /opt/mambaforge/envs/mwe/bin/python
version: '3.11'