Configure TimeSeries Decimal Precision

The Precision Problem: When 3 Digits Just Aren't Enough

Have you ever run into a frustrating situation where your exported TimeSeries data just doesn't quite match what you expect, especially when it comes to decimal places? If you're working with OpenDCS, you might have noticed that the TimeSeries export feature currently hardcodes a limit of 3 fraction digits. This might sound like a small detail, but in the world of data analysis and testing, it can cause significant headaches. Specifically, the outputts.bat script relies on this hardcoded formatter. This means that your expectedOutputs .tsimport files end up with values that have been rounded to three decimal places. Now, here's where the real pain begins: integration tests often depend on a very specific tolerance, like DEFAULT_DELTA = 0.0001 found in assertions\TimeSeries.java. When your exported data is rounded to just three decimal places (e.g., showing 0.001 instead of a more precise 0.0006), these tests will inevitably fail. This discrepancy, while seemingly minor, can halt your testing process and create a barrier to seamless data integration and validation. We need a way to ensure that the precision of our exported data aligns perfectly with the precision required by our tests and other downstream processes.

The Solution: Unleash Configurable Decimal Precision

Our proposed solution is straightforward yet powerful: make the maximum fraction digits for TimeSeries export a configurable option. Imagine a world where you can easily set how many decimal places you want in your exported data, without needing to dive into the code itself. We suggest defaulting this new configuration to 4 decimal places. Why 4? Because this aligns perfectly with the 0.0001 precision used in the DEFAULT_DELTA for our tests. This simple change would immediately resolve the common testing failures caused by rounding issues. By making this a configurable setting, users gain the flexibility to adapt the export precision to their specific needs, whether it's for detailed analysis, regulatory compliance, or simply ensuring test integrity. This isn't just about accommodating tests; it's about empowering users with greater control over their data exports, leading to more reliable results and a smoother workflow overall. Think of it as giving your data the right level of detail it deserves.

Exploring Alternatives: What Else Did We Consider?

Before landing on the idea of a direct configuration for decimal places, we explored a few other avenues. One initial thought was to leverage existing settings. We looked at DecodesSettings and user.properties, which have a defaultMaxDecimals setting, often defaulting to 4. However, in practice, we found that changing this particular setting didn't actually influence the TimeSeries formatting during exports. It seemed to be bypassed or overridden by the hardcoded value. Another simpler, albeit less elegant, approach was to simply hardcode a larger value directly into the TimeSeries.java file, ensuring it was at least 4 or more. While this would work as a short-term fix to match the DEFAULT_DELTA, it lacks flexibility. If requirements change or if different parts of the system need varying levels of precision, we'd be back to square one, needing to modify the code again. We also investigated using DataPresentation entries within cwms-import.xml. This approach is quite powerful for controlling precision in Run Computations plots and tables, allowing specific MaxDecimals settings per DataType, like setting EvapRate to 2 decimals while Evap gets 4. However, the outputts utility still relied on the hardcoded formatter, meaning this XML configuration didn't solve the export precision issue for that specific tool. Even fiddling with units, like changing EvapRate from mm/day to mm/hr, only affected the UI display. When saving output data, the system still used the database unit (mm/day), limiting the effectiveness of unit-based precision control for exports. These alternatives showed us that a direct, user-facing configuration for export decimal precision was the most robust and flexible solution.

Beyond Digits: Precision and Unit Handling

While the primary focus of this enhancement is on controlling the precision of exported TimeSeries data, it's worth acknowledging that unit handling also plays a role in how data is perceived and utilized. In some scenarios, the desired precision might be intrinsically linked to the units being used. For instance, a rate measured in millimeters per hour might require a different decimal precision than the same rate measured in millimeters per day. Our current exploration into making fraction digits configurable directly addresses the precision need, ensuring that exported values can match test tolerances and analytical requirements. However, a broader enhancement could also involve more sophisticated unit management during export. This might include options to export data in a different unit than its native database unit, provided a conversion is possible. This would not only help in aligning data with specific downstream applications but could also indirectly influence the perceived precision by choosing units that are more appropriate for the magnitude of the values. For example, exporting a very small flow rate in liters per second might be less intuitive than exporting it in milliliters per second, which might then require fewer decimal places for clarity. While unit conversion and selection are secondary to the immediate need for configurable decimal precision, they represent valuable complementary features that could further enhance the utility and flexibility of OpenDCS exports. For now, though, the ability to directly control the number of fraction digits is the most critical step towards resolving export discrepancies and ensuring data integrity across different parts of the OpenDCS ecosystem. This will allow tests and exports to align seamlessly, eliminating the need for code edits or complex unit workarounds and providing a much smoother user experience.

Conclusion: A Small Change for Big Impact

Implementing a configurable option for TimeSeries decimal precision in OpenDCS exports is a crucial step towards improving data integrity and streamlining workflows. By allowing users to set the maximum number of fraction digits, we directly address the common issues encountered with integration testing and data export consistency. This enhancement moves away from rigid, hardcoded values towards a flexible, user-centric approach. It means that your exported data will accurately reflect the precision required by your analyses and tests, eliminating the frustrating discrepancies caused by unnecessary rounding. This change promises to save valuable time, reduce debugging efforts, and ultimately lead to more reliable results when working with time-series data. We believe this feature will be a significant benefit to the OpenDCS community, making data handling more robust and user-friendly.

For more insights into data handling and time-series analysis, you can explore resources from organizations like the U.S. Geological Survey (USGS), which offers extensive information on water data and hydrological analysis, or consult the documentation on time series databases to understand best practices in managing time-stamped data.