Update README.md

Added information about the MNIST dataset.

README.md

@@ -45,3 +45,24 @@ mX = np.reshape(tX, (tX.shape[0], -1))
 dfData = pd.DataFrame(np.concatenate((mX, vY[:, np.newaxis]), axis = 1), columns = [f'Pixel_{ii:04d}' for ii in range(mX.shape[1])] + ['Label'])
 dfData.to_parquet('CIFAR10.parquet', index = False)
 ```
+
+### MNIST
+
+A dataframe where the first 60,000 rows are the train set and the last 10,000 are the test set.  
+The last column is the label.  
+Images are row major, hence a `np.reshape(dfX.iloc[0, :-1], (28, 28))` will generate the image. 
+
+Generated by:
+
+```python
+import numpy as np
+from sklearn.datasets import fetch_openml
+
+dfX, dsY = fetch_openml('mnist_784', version = 1, return_X_y = True, as_frame = True)
+
+dfX.columns = [f'{ii:04d}' for ii in range(dfX.shape[1])]
+dfX['Label'] = dsY.astype(np.uint8)
+dfX = dfX.astype(np.uint8)
+
+dfX.to_parquet('MNIST.parquet', index = False)
+```