# What is Multivariate time series forecasting

##### Understanding Multivariate Time Series Forecasting

Time series forecasting is a popular area of research in machine learning and artificial intelligence. It involves using historical data to make predictions about future events or values. Multivariate time series forecasting is a subfield of time series forecasting that deals with datasets that have more than one variable.

For example, a dataset might contain information about the temperature, humidity, and wind speed at a particular location over a period of time. Multivariate time series forecasting algorithms can use this data to predict future values of all three variables.

In this article, we'll take a closer look at multivariate time series forecasting, including some of the challenges involved and some of the techniques and algorithms used in this field.

##### Challenges of Multivariate Time Series Forecasting

One of the main challenges of multivariate time series forecasting is dealing with the relationships between the variables in the dataset. In many cases, the variables are not independent of each other, meaning that changes in one variable can influence the values of other variables.

Another challenge is dealing with missing data. Multivariate time series datasets are often incomplete, with missing values for some of the variables at certain time steps. This can make it more difficult to build accurate models and make accurate predictions.

##### Techniques for Multivariate Time Series Forecasting

There are several techniques that are commonly used in multivariate time series forecasting. Some of these techniques include:

• Vector Autoregression (VAR): This is a popular statistical technique for multivariate time series forecasting. It involves modeling each variable in the dataset as a linear combination of lagged values of all the variables in the dataset.
• Long Short-Term Memory (LSTM): This is a type of recurrent neural network (RNN) that is often used for time series forecasting. LSTMs can handle complex relationships between variables and can capture long-term dependencies in the data.
• Random Forests: This is an ensemble learning method that can be used for predicting multivariate time series data. Each tree in the random forest is trained on a random subset of the input variables, which can help to reduce overfitting and improve accuracy.
##### VAR for Multivariate Time Series Forecasting

Let's dive deeper into the VAR model for multivariate time series forecasting. The VAR model is a linear model that can capture the relationships between multiple time series variables. It assumes that each variable in the dataset is a function of its own lagged values and the lagged values of all the other variables in the dataset.

The VAR model can be represented mathematically as:

Yt = A1Yt-1 + A2Yt-2 + … + ApYt-p + εt

where Yt is a vector of the values of all the variables at time t, A1 … Ap are matrices of coefficients that capture the relationships between the variables, p is the order of the VAR model, and εt is a vector of error terms.

The VAR model can be used to make predictions about the values of all the variables in the dataset at future time steps. To make a prediction for time t+1, we can use the VAR model to predict the values of all the variables at time t+1 based on the values of all the variables at time t and the lagged values of all the variables up to time t-p.

##### LSTM for Multivariate Time Series Forecasting

LSTM is another popular technique for multivariate time series forecasting. LSTM is a type of recurrent neural network that can capture long-term dependencies in sequential data. Unlike traditional feedforward neural networks, LSTM networks have loops that allow information to flow from one step of the network to the next.

Each node in an LSTM network has a cell state, which allows it to retain information over multiple time steps. The network can selectively forget or remember information based on input data and its current state.

In multivariate time series forecasting, each node in an LSTM network represents a variable in the dataset, and the network is trained to predict all the variables at each time step. The input to the network at each time step is a vector of the values of all the variables at that time step, and the output of the network is a vector of predicted values for all the variables at the next time step.

##### Random Forests for Multivariate Time Series Forecasting

Random forests are another popular technique for multivariate time series forecasting. Random forests are an ensemble learning method that combines multiple decision trees to make predictions.

Each tree in a random forest is trained on a different random subset of the input variables and a different random subset of the training data. This helps to reduce overfitting and improve the accuracy of the model.

For multivariate time series forecasting, each tree in the random forest can predict the values of all the variables in the dataset at a single time step. The results of all the trees can be combined to make a final prediction for all the variables at each time step.

##### Conclusion

Multivariate time series forecasting is a complex field that requires careful consideration of the relationships between the variables in the dataset. Techniques like VAR, LSTM, and random forests can be used to make accurate predictions about the future values of multiple variables.

When building models for multivariate time series forecasting, it's important to carefully analyze the data and choose the right model for the specific problem and dataset at hand. With the right techniques and algorithms, it's possible to make accurate predictions about complex time series data.