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Combining Reconciliation and Conformal Prediction for Better Forecasts

A new approach improves forecasting accuracy through Reconciliation and Conformal Prediction.

Guillaume Principato, Yvenn Amara-Ouali, Yannig Goude, Bachir Hamrouche, Jean-Michel Poggi, Gilles Stoltz

― 6 min read


Advancing Forecast Advancing Forecast Accuracy reliability across various fields. A new method enhances prediction
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In the world of forecasting, we often deal with numbers in a structured way. Think of it like stacking blocks in different shapes. Each block represents a certain level of data: you have houses, neighborhoods, cities, and so on. Sometimes, predicting how much electricity a house will use on a hot summer day can be as tricky as predicting the total demand for the entire city. This is where a fancy method called "Reconciliation" comes in handy.

What’s the Deal with Reconciliation?

Imagine you made a guess about how much a particular sandwich shop will sell. Now, that guess might not match up with the total sales from all the sandwich shops in town. Reconciliation helps to align those guesses, making sure that the overall picture makes sense.

In simpler terms, it’s like herding cats. You want all those cat predictions to come together nicely instead of running in different directions. In many real-life situations, like power consumption Forecasts, these structures are vital. If one house is using more power than expected, it can ripple through the system.

A Sneak Peek into Conformal Prediction

Now, let’s throw another fancy term into the mix: Conformal Prediction. This method helps us generate a set of possible predictions, rather than just one. This means if we guess that a sandwich shop will sell between 50 and 75 sandwiches, we’re not just saying, "It must be 60." Instead, we’re saying, "It could be anywhere in this range, but we feel pretty good about it."

This framework has been gaining popularity because it offers a reliable way to deal with uncertainty. Instead of throwing out an educated guess and hoping for the best, it gives you a safety net. You still might land on your face, but at least you know there’s a soft landing somewhere in that range.

The Magic of Combining Reconciliation and Conformal Prediction

Now, what happens when you combine Reconciliation and Conformal Prediction? Well, it’s like mixing peanut butter and jelly. Each flavor adds something special, and together they create a delicious outcome. By using Reconciliation within the Conformal Prediction framework, we can create more reliable forecasts.

We discovered that when predictions from different levels (like houses, neighborhoods, and cities) are reconciled before applying Conformal Prediction, the predictions become not only valid but also more effective. It’s like getting a group of friends together to agree on a restaurant. When everyone’s input is considered, the chances of ending up at a great place increase.

Breaking it Down: Hierarchical Time Series

Let’s take a closer look at what we mean by hierarchical time series. Picture a tree, where each branch represents different levels of data. The leaves of this tree contain the most specific data. For instance, if we’re looking at how much energy a particular neighborhood uses, we can also consider how much energy the entire city uses.

Now, when we’re predicting energy usage based on data from all levels, we need to make sure that all our predictions are in sync. If the city-wide forecast says the total power consumption will be 10,000 kilowatts and the neighborhood’s forecast says 15,000 kilowatts, something's amiss!

The Challenge: Getting It Right

When we gather data to make these forecasts, we face a challenge: ensuring that the data at all levels match up. It's vital for our predictions to work in harmony. If we want a reliable forecast for a neighborhood, we might need to pull in information from the entire city as well.

But here’s the kicker: how do we quantify this harmony? Traditional methods might not cut it, especially when you’re trying to be precise about probabilistic forecasting. We need to blend the insights we get from individual forecasts while keeping an eye on the big picture.

Enter the New Approach: Reconciled Conformal Prediction

Through our work, we cook up a method called reconciled conformal prediction, which smartly combines these ideas. We start by predicting the forecasts for each individual level. Once we have those, we make sure they align with the overall forecast. It’s kind of like confirming that every cat in the herd is heading in the same direction.

When we test this approach, we find that the prediction sets we generate offer better coverage. This means we’re more successful at capturing the true values within our predicted ranges, thus providing a more robust safety net.

Why are We So Excited About This?

So, why do we think this approach is a game-changer? It gives us a practical tool to make sense of complex, layered forecasts without losing sight of the individual components. Imagine trying to bake a cake without knowing how all the ingredients will interact. That can lead to a cake that’s either too dry or full of air bubbles.

By leveraging both the Reconciliation technique and Conformal Prediction, we create a better cake! Not only does it taste good, but it also looks fantastic. We can apply this to various fields, from weather predictions to stock market forecasts, ensuring we have a solid grip on probabilities.

Making It Practical

Of course, the magic lies in how we implement these methods. In practice, we need to be able to split our data wisely, ensuring that we capture enough to get good statistical estimates. We also need to run validations to see how well our predictions pan out. Think of this as practice sessions before the big game.

A Peek into Our Experiments

In our experiments, we create a synthetic dataset that reflects how hierarchical time series behave. This lets us test our method under various conditions. We simulate different levels of data and try to predict how well our reconciled conformal prediction stacks up against regular methods.

As we run our simulations, we monitor how well we can capture the “true” sales of our sandwich shop. Can we reliably predict whether they will sell 50 or 60 sandwiches? Our approach hones in on this goal while keeping the hierarchical structure intact.

The Takeaway

What we find is exciting. Reconciled Conformal Prediction gives us a way to blend individual forecasts while ensuring they make sense when viewed together. This is no small feat, and the implications stretch far and wide.

Whether it’s energy consumption, sales forecasting, or even predicting the weather, this approach holds tremendous potential. It empowers decision-makers with reliable data, which in turn helps them make informed choices.

So there you have it! Just like the perfect PB&J sandwich, when you mix the right ingredients, you get something that not only tastes great but also delivers on every level. We can’t wait to see where this research leads us, and we're hopeful that our findings will make a big splash in various industries. After all, who doesn’t want better forecasts, right?

Original Source

Title: Conformal Prediction for Hierarchical Data

Abstract: Reconciliation has become an essential tool in multivariate point forecasting for hierarchical time series. However, there is still a lack of understanding of the theoretical properties of probabilistic Forecast Reconciliation techniques. Meanwhile, Conformal Prediction is a general framework with growing appeal that provides prediction sets with probabilistic guarantees in finite sample. In this paper, we propose a first step towards combining Conformal Prediction and Forecast Reconciliation by analyzing how including a reconciliation step in the Split Conformal Prediction (SCP) procedure enhances the resulting prediction sets. In particular, we show that the validity granted by SCP remains while improving the efficiency of the prediction sets. We also advocate a variation of the theoretical procedure for practical use. Finally, we illustrate these results with simulations.

Authors: Guillaume Principato, Yvenn Amara-Ouali, Yannig Goude, Bachir Hamrouche, Jean-Michel Poggi, Gilles Stoltz

Last Update: Nov 20, 2024

Language: English

Source URL: https://arxiv.org/abs/2411.13479

Source PDF: https://arxiv.org/pdf/2411.13479

Licence: https://creativecommons.org/licenses/by/4.0/

Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.

Thank you to arxiv for use of its open access interoperability.

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