CSV/Excel ↔ ARFF Converter

Our converter analyzes each column in your data to determine the most appropriate attribute type:

• Numeric: Columns containing only numbers (integers or decimals)
• Nominal: Columns with a limited set of distinct string values (less than 20 unique values)
• String: Columns with mostly unique text values or long text
• Date: Columns with values that match common date formats

You can review and manually adjust these detections before final conversion if needed.

Our converter supports the following formats:

• Input: CSV (.csv), Excel (.xlsx, .xls), ARFF (.arff)
• Output: ARFF (.arff), CSV (.csv), Excel (.xlsx)

For CSV files, you can specify the delimiter (comma, semicolon, tab, pipe, or custom character).

Missing values are handled according to the ARFF specification:

• When converting to ARFF, empty cells or cells with "NA", "N/A", "null", or "?" are converted to "?" in the ARFF file
• When converting from ARFF, "?" values are converted to empty cells in CSV/Excel or can be replaced with a specified value

This ensures compatibility with machine learning algorithms that expect standard missing value notation.

Our web-based converter can handle files up to 50MB in size. For larger files:

• Consider using batch mode to process the file in chunks
• For very large datasets, we recommend using Weka's command-line tools directly
• All processing happens in your browser - your data never leaves your computer

After converting your data to ARFF format:

1. Open Weka Explorer
2. Click "Open file" and select your ARFF file
3. The data will load with all attribute types properly defined
4. You can now use all of Weka's preprocessing and machine learning tools

Our converter ensures the ARFF file follows Weka's specifications exactly, including proper relation names, attribute declarations, and data formatting.