ttest() TypeError: object of type 'int' has no len()

[benpla]

The first sample code fails with:

Code:

from pingouin import ttest
x = [5.5, 2.4, 6.8, 9.6, 4.2]
ttest(x, 4).round(2)

Every try for ttest farls with the same wessage.
Avova works as expected.
I enter code as simple as possible, but I can not understand the error message.

I uninstalled pingouin using conda remove pingouin.
Then installation with pip. Same result.
I installed an older version (conda install -c conda-forge/label/cf202003 pingouin).
Same result.

What can be the reason for this?

Here is my output:

(py39v1) bp@bplattemac ~ % python
Python 3.9.7 (default, Sep 16 2021, 08:50:36) 
[Clang 10.0.0 ] :: Anaconda, Inc. on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from pingouin import ttest
>>> x = [5.5, 2.4, 6.8, 9.6, 4.2]
>>> ttest(x, 4).round(2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/bp/opt/anaconda3/envs/py39v1/lib/python3.9/site-packages/pingouin/parametric.py", line 309, in ttest
    stats = pd.DataFrame.from_records(stats, columns=col_order, index=['T-test'])
  File "/Users/bp/opt/anaconda3/envs/py39v1/lib/python3.9/site-packages/pandas/core/frame.py", line 2215, in from_records
    arrays, arr_columns, result_index = maybe_reorder(
  File "/Users/bp/opt/anaconda3/envs/py39v1/lib/python3.9/site-packages/pandas/core/frame.py", line 2165, in maybe_reorder
    length = len(arrays[0])
TypeError: object of type 'int' has no len()
>>> 

[Pofozaur]

same issue here

>>> import numpy as np
>>> import pingouin as pg
>>> np.random.seed(123)
>>> mean, cov, n = [4, 5], [(1, .6), (.6, 1)], 30
>>> x, y = np.random.multivariate_normal(mean, cov, n).T
>>> pg.ttest(x, y)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/kamil/test/venv/lib/python3.8/site-packages/pingouin/parametric.py", line 309, in ttest
    stats = pd.DataFrame.from_records(stats, columns=col_order, index=['T-test'])
  File "/home/kamil/test/venv/lib/python3.8/site-packages/pandas/core/frame.py", line 2215, in from_records
    arrays, arr_columns, result_index = maybe_reorder(
  File "/home/kamil/test/venv/lib/python3.8/site-packages/pandas/core/frame.py", line 2165, in maybe_reorder
    length = len(arrays[0])
TypeError: object of type 'int' has no len()
>>>

Python 3.8.10

Package            Version  
------------------ ---------
certifi            2021.10.8
charset-normalizer 2.0.10   
cycler             0.11.0   
fonttools          4.28.5   
idna               3.3      
joblib             1.1.0    
kiwisolver         1.3.2    
littleutils        0.2.2    
matplotlib         3.5.1    
numpy              1.22.1   
outdated           0.2.1    
packaging          21.3     
pandas             1.4.0    
pandas-flavor      0.2.0    
patsy              0.5.2    
Pillow             9.0.0    
pingouin           0.5.0    
pip                20.0.2   
pkg-resources      0.0.0    
pyparsing          3.0.7    
python-dateutil    2.8.2    
pytz               2021.3   
requests           2.27.1   
scikit-learn       1.0.2    
scipy              1.7.3    
seaborn            0.11.2   
setuptools         44.0.0   
six                1.16.0   
statsmodels        0.13.1   
tabulate           0.8.9    
threadpoolctl      3.0.0    
urllib3            1.26.8   
xarray             0.20.2

[Pofozaur]

it's looks like issue with numpy or pandas

@benpla if you want quickfix for this problem, install numpy==1.21.5 and pandas==1.3.5 before installing pingouin

[benpla]

@Pofozaur : Your suggestion did the trick!

First remove packages:

conda remove pingouin, numpy, pandas

Which Versions are installable?

conda search --override-channels --channel conda-forge numpy
conda search --override-channels --channel conda-forge pandas

On conda-forge channel the suggested versions are available.
Now install:

conda install -c conda-forge numpy=1.21.5
conda install -c conda-forge pandas=1.3.5
conda install -c conda-forge pingouin

Run python with test().... and voila: it works!
Thanks!

[raphaelvallat]

Hi,

Thanks for opening the issue. The error is related to the latest release of Pandas (1.4.0), which leads to an error here:

pingouin/pingouin/parametric.py

Line 309 in dcfdc82

stats = pd.DataFrame.from_records(stats, columns=col_order, index=['T-test'])

A simple fix is to replace the above line with:

stats = pd.DataFrame(stats, columns=col_order, index=['T-test'])  # works with pandas 1.4.0

I'll implement this in the next release of Pingouin. In the meantime, a quick fix is to revert to pandas 1.3.5:

pip install pandas==1.3.5

Thanks,
Raphael