How to convert .mat file into csv using python?

Question

I have used this code first-

from scipy.io import loadmat 
data=loadmat(r"C:\Users\ansha\Downloads\HTS_C1_SN14_13.11.2019_02.mat")
print(data.keys())

and then i got this as an output-

dict_keys(['__header__', '__version__', '__globals__', 'EyePts_', 'JoyPts_', 'TrlNo_', 'M1EyeX_', 'M1EyeY_', 'M1Pupil_', 'M1JoyX_', 'M1JoyY_', 'cond_', 'RwdCue_', 'MagCue_', 'MLTrialStart_', 'MLTrialEnd_', 'TrialStart_', 'FixToggleON_', 'FixON_', 'AcqFix_', 'HoldFix_', 'Correct_', 'RewardONJ1_', 'RewardOFFJ1_', 'Abort_', 'EndOfTrial_', 'ITION_', 'ITIOFF_', 'STargetON_', 'AcqSTarget_', 'HoldSTarget_', 'SmRwdON_', 'SmRwdOFF_', 'LickCamON_', 'RewardCueON_', 'HoldRwdCue_', 'MagnitudeCueON_', 'HoldMagCue_', 'TwoTargetsON_', 'AcqRTarget_', 'HoldRTarget_', 'AcqLTarget_', 'HoldLTarget_', 'RewardONJ2_', 'RewardOFFJ2_', 'RewardONJ3_', 'RewardOFFJ3_', 'RewardONJ4_', 'RewardOFFJ4_', 'YRcue_pos_', 'WRcue_pos_', 'LT_pos_', 'RT_pos_', 'RT_col_', 'LT_col_', 'RCueCol_', 'JoyPosn_', 'LeftT_', 'RtT_', 'ReactionTime_', 'ReactionTimeP_'])

I am now lost, and i do not know how to convert this into a pandas dataframe and save it as csv. Please help!!!

Will · Accepted Answer · 2022-08-29 12:42:30Z

3

Try Using:

from scipy.io import loadmat 
import pandas as pd
data = loadmat(r"C:\Users\ansha\Downloads\HTS_C1_SN14_13.11.2019_02.mat")
data  = {k:v for k, v in data.items() if k[0] != '_'}
df = pd.DataFrame({k: pd.Series(v[0]) for k, v in data.items()})  
df.to_csv("example.csv")

edited Aug 29, 2022 at 12:42

answered Aug 29, 2022 at 11:56

Will

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5 Comments

Ansh Bharadwaj Over a year ago

it is giving me this error- NameError Traceback (most recent call last) Input In [5], in <cell line: 4>() 2 import pandas as pd 3 data=loadmat(r"C:\Users\ansha\Downloads\HTS_C1_SN14_13.11.2019_02.mat") ----> 4 mat={k:v for k,v in mat.items() if k[0]!="_"} 5 data=pd.DataFrame({k:pd.Series(v[0])for k ,v in mat.items()}) 6 data.to_csv("IITK.csv") NameError: name 'mat' is not defined

Will Over a year ago

try now. I changed the variable name.

Ansh Bharadwaj Over a year ago

i think it worked but where do i find the csv file now? or how do i see the csv file? i am sorry i am just a newbie here!!!

Ansh Bharadwaj Over a year ago

oh wait, i now found it! thanks a ton for your help!!

Will Over a year ago

@AnshBharadwaj if the answer is correct upvote it and mark as correct by clicking the tick under the down arrow

sidharth dk · Accepted Answer · 2025-09-02 13:00:09Z

import os
import scipy.io
import pandas as pd
import numpy as np

# Direct path to your Matlab folder
matlab_folder = r"your file path " #add the path to your file
output_folder = os.path.join(os.path.dirname(matlab_folder), "outputs")
os.makedirs(output_folder, exist_ok=True)

def to_dataframe(var_data, var_name):
    arr = np.array(var_data)
    if arr.ndim == 1:
        return pd.DataFrame({var_name: arr})
    elif arr.ndim == 2 and arr.shape[1] == 1:
        return pd.DataFrame({var_name: arr.ravel()})
    elif arr.ndim == 2:
        cols = [f"{var_name}_{i}" for i in range(arr.shape[1])]
        return pd.DataFrame(arr, columns=cols)
    else:
        flat = arr.reshape(arr.shape[0], -1)
        cols = [f"{var_name}_{i}" for i in range(flat.shape[1])]
        return pd.DataFrame(flat, columns=cols)

# Convert all .mat files inside the Matlab folder
for file in os.listdir(matlab_folder):
    if file.endswith(".mat"):
        file_path = os.path.join(matlab_folder, file)
        print(f"⚙ Processing {file_path}...")

        data = scipy.io.loadmat(file_path)
        clean_data = {k: v for k, v in data.items() if not k.startswith("")}

        base_name = os.path.splitext(file)[0]
        csv_path = os.path.join(output_folder, f"{base_name}.csv")
        xlsx_path = os.path.join(output_folder, f"{base_name}.xlsx")

        all_dfs = []

        with pd.ExcelWriter(xlsx_path, engine="openpyxl", mode="w") as writer:
            for var_name, var_data in clean_data.items():
                try:
                    df = to_dataframe(var_data, var_name)
                except Exception:
                    df = pd.DataFrame({var_name: [str(var_data)]})

                # Save each variable to its own Excel sheet
                df.to_excel(writer, sheet_name=var_name[:31], index=False)

                # Collect for CSV merge
                all_dfs.append(df)

        if all_dfs:
            final_df = pd.concat(all_dfs, axis=1)
            final_df = final_df.applymap(lambda x: x if np.isscalar(x) else str(x))
            final_df.to_csv(csv_path, index=False)

        print(f"✔ Converted {file} → {csv_path}, {xlsx_path}")

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