Python Matlab engine: How to pass a pandas dataframe to Matlab function?

29 次查看（过去 30 天）
Stefan
Stefan 2024-5-29
评论： Stefan 2024-5-29
Hi everyone,
I'd like to pass a Python Pandas dataframe to a Matlab function. E.g.:
>>> DATAFILE = "2024-05-28_11-30-06.parquet"
>>> import matlab.engine
>>> import pandas as pd
>>> eng = matlab.engine.start_matlab()
>>> df = pd.read_parquet(DATAFILE)
>>> eng.table(df)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:\Users\someone\venv\matlab2\Lib\site-packages\matlab\engine\matlabengine.py", line 64, in __call__
future = pythonengine.evaluateFunction(self._engine()._matlab,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: unsupported Python data type: pandas.core.frame.DataFrame
Do I miss a conversion step?
Doing the same from Matlab works:
>> pyenv('Version','C:\Users\someone\venv\matlab2\Scripts\python.exe','ExecutionMode','OutOfProcess')
ans =
PythonEnvironment with properties:
Version: "3.11"
Executable: "C:\Users\someone\venv\matlab2\Scripts\python.exe"
Library: "C:\Users\someone\AppData\Local\Programs\Python\Python311\python311.dll"
Home: "C:\Users\someone\venv\matlab2"
Status: NotLoaded
ExecutionMode: OutOfProcess
>> df = py.pandas.read_parquet("2024-05-28_11-30-06.parquet");
>> t = table(df)
t =
300000×6 table
Thanks in advance!
Best regards,
Stefan

请先登录，再回答此问题。

回答（1 个）

Akshat
Akshat 2024-5-29
Hi Stefan,
I see you are trying to make a MATLAB table out of a pandas Dataframe object using the MATLAB engine for python.
You're approach is more or less accurate, just leaving out one thing which I found out from this documentation page:
https://www.mathworks.com/help/matlab/matlab_external/python-pandas-dataframes.html
Now in this, it is using the python connector in MATLAB, but I saw the line where they are first typecasting the dataframe to a struct, and then making a table.
Looking at that, I tried making a struct first, but I got the same error. Somehow, we need to first convert the dataframe into a dictionary (using "df.to_dict()" documentation here : https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.to_dict.html). I used the 'records' argument.
Then, it successfully converted into a MATLAB Object!
PFA the screenshot.
Hope this helps!
  1 个评论
Stefan
Stefan 2024-5-29
Hi Akshat,
I just tested your solution. It works but it is very slow. My example dataframe took 85 seconds. Just to compare:
eng.eval("pyenv('Version','C:\\Users\\someone\\venv\\matlab2\\Scripts\\python.exe','ExecutionMode','OutOfProcess')", nargout=0)
fname = "C:\\temp\\file.parquet"
df.to_parquet(fname) # write pandas dataframe to disk
dfm = eng.py.pandas.read_parquet(fname) # python - matlab -python to read it again
t = eng.table(dfm)
took 1.7 seconds. So writing dataframe to disk, reading it from disk and converting it to Matlab table was more than 40 times faster. So there hopefully is a shortcut without writing things to disk.
Best regards,
Stefan

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Call Python from MATLAB 的更多信息

标签

产品


版本

R2024a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by