KR101901654B1

KR101901654B1 - System and method for time-series predicting using integrated forward and backward trends, and a recording medium having computer readable program for executing the method

Info

Publication number: KR101901654B1
Application number: KR1020150184798A
Authority: KR
Inventors: 안도훈; 이기천; 이운섭
Original assignee: (주) 우림인포텍; 한양대학교 산학협력단
Priority date: 2015-12-23
Filing date: 2015-12-23
Publication date: 2018-09-27
Also published as: KR20170075312A

Abstract

A forward predicted data calculating unit, a forward predicted data calculating unit, a forward predicted data calculating unit, a forward predicted data calculating unit, a forward predicted data calculating unit, a time-series data input unit, a forward directional arithmetic analysis model building unit, . And the first predictive data calculating unit calculates a first predictive data for the future using the forward directional arithmetic analysis model based on the time series data, Data is calculated and the reverse arithmetic model is constructed by using the reverse arithmetic model building part in the reverse direction using the reverse arithmetic model building part and the learning data calculating part calculates the fitted data using the reverse arithmetic analysis model, The second predictive data calculation unit calculates second predictive data for a future time point set in advance using the proximity prediction model, and the final predictive data calculation unit calculates The first prediction date And the second predicted data are combined to calculate final predicted data.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system and method for predicting forward and backward directional integrated time series, and a recording medium storing a computer readable program for executing the method. BACKGROUND OF THE INVENTION 1. Field of the Invention EXECUTING THE METHOD}

The present invention relates to time series analysis methods and systems, and more particularly, to a method and system for predicting future data using time series analysis.

Time series analysis is a field that analyzes the observed data with time. The most interesting part of the time series analysis is the prediction, and the time series analysis assumes that the pattern of the changes obtained from the past data will be maintained in the future and is a scientific prediction analysis. Currently, time-related data such as demographics, financial markets or weather forecasts are used in many industries where it is used.

The most widely used analytical model for time series prediction is ARIMA (AutoRegressive Integrated Moving Average). The Arima model is generally useful in short-term predictions and is useful when the components of a time series fluctuate rapidly over time, and is used in various industries.

However, in ARIMA model, if there is a sudden change in factors such as abnormal weather or holiday, like the price of agricultural and marine products, even if a new model is built to reflect this effect, there is a phenomenon that the prediction of the model follows the actual change late, There is a problem of lowering.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for estimating a model predicted by a model that can rapidly follow actual changes and improve predictive power even when sudden changes such as abnormal weather or holidays occur, System, and method.

In order to achieve the above object, a time series prediction system according to the present invention includes a time series data input unit, a forward directional arithmetic analysis model building unit, a first prediction data calculation unit, a reverse directional arithmetic model building unit, a fitting data calculation unit, A second prediction data calculation unit, and a final prediction data calculation unit.

And the first predictive data calculating unit calculates a first predictive data for the future using the forward directional arithmetic analysis model based on the time series data, And the reverse arithmetic model building unit constructs a reverse arithmetic analysis model using the time series data in the reverse direction, the matching data calculating unit calculates fitted data using the reverse arithmetic analysis model, and the proximity prediction model building unit The second prediction data calculation unit calculates second prediction data for a future time point set in advance using the proximity prediction model, and the final prediction data calculation unit calculates the second prediction data using the proximity prediction model, The first prediction date And the second predicted data are combined to calculate final predicted data.

This arrangement allows the forward ARIMA model to be influenced by future forecasts of the ARIMA model in the reverse order of time so that even if there is a sudden change in factors such as weather, The prediction of the model can follow the actual change quickly and increase the predictive power.

At this time, the proximity prediction model using the non-parametric analysis method may be a locally weighted polynomial regression (LOESS) analysis model. According to this configuration, the future prediction can be performed by reflecting the prediction trend of the reverse arithmetic analysis model using the characteristic of the LOESS model which places a lot of weight on the data of the adjacent section.

Also, the final prediction data can be calculated using the weighted average of the first prediction data and the second prediction data.

The time series prediction system further includes a prediction data evaluation unit for evaluating the final prediction data and a smoothing parameter changing unit for changing the smoothing parameter of the local weighted polynomial analysis model when the final prediction data is out of the preset evaluation reference . According to this configuration, the setting of the prediction model can be adjusted in accordance with the prediction result to construct an optimum prediction model.

At this time, the prediction data evaluation unit may compare the final prediction data with the first prediction data, and may compare the final prediction data calculated using different smoothing parameters with each other.

The apparatus may further include a time series data separator for separating the data used for calculating the final predictive data from the time series data and the evaluation data used for evaluating the final predictive data. According to this configuration, it is possible to perform prediction of future prediction as well as prediction using input time series data.

The time series data preprocessing unit may further include a time series data preprocessing unit for detecting and replacing an abnormal value in the input time series data, and the abnormal value detection and replacement in the time series data may be performed by a spline method. According to such a configuration, it is possible to perform more effective prediction by excluding an ideal value that greatly affects the prediction result from the input time series data.

In addition, the invention in which the system is implemented in the form of a method and a computer readable program for executing the method are disclosed together.

According to the present invention, by adding the influence of the future prediction of the ARIMA model to the ARIMA model in the reverse order of time, even when there is a sudden change in factors such as abnormal weather or holidays, Predicts the actual change quickly, thereby increasing the predictive power.

Also, using the features of the LOESS model, which weights a lot of data in the adjacent segments, future predictions can be made by reflecting the trend of the reverse arithmetic analysis model.

In addition, it is possible to construct an optimum prediction model by adjusting the setting of the prediction model according to the prediction result.

In addition, it is possible to evaluate prediction results as well as future predictions using input time series data.

Further, by excluding an ideal value having a large influence on the prediction result from the input time series data, more effective prediction can be performed.

1 is a schematic block diagram of a time-series prediction system in accordance with an embodiment of the present invention.
Figure 2 is a schematic flow diagram of a time series prediction method performed by the system of Figure 1;
Figure 3 is a more specific flow chart of Figure 2;
4 is a graph showing an example of replacing an ideal value due to an input error with a spline value.
FIG. 5 is a graph showing an example of a Forward ARIMA analysis and prediction of 5 days.
FIG. 6 is a graph showing an example in which backward ARIMA analysis is performed in the reverse direction of time.
FIG. 7 is a graph illustrating an example in which fit data learned in the model of FIG.
8 is a graph showing the results of repeatedly performing LOESS analysis using different parameters a (span).

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a schematic block diagram of a time-series prediction system according to an embodiment of the present invention.

1, the time series prediction system includes a time series data input unit 110, a time series data preprocessing unit 120, a time series data separating unit 130, a forward directional arithmetic analysis model building unit 140, A second predictive data calculation unit 190, a final predictive data calculation unit 200, and a second predictive data calculation unit 140. The first predictive data calculation unit 150, the second predictive data calculation unit 160, A prediction data evaluation unit 210, and a parameter changing unit 220.

In FIG. 1, each component of the time series prediction system 100 may be implemented in hardware, but it may be more general to be implemented in software that operates on hardware.

The time series data input unit 110 receives the time series data, and the time series data preprocessing unit 120 detects and replaces the abnormal value in the input time series data.

There are many outliers in the data input by man, such as agricultural auction price data. According to the time-series data preprocessing unit 120, it is possible to perform more effective prediction by excluding an ideal value that greatly affects the prediction result from the input time series data.

In order to search for outliers, we perform spline analysis similar to the trend of time series, find data whose difference between the actual data value and the spline value is above the threshold value, determine the found data as the outlier value, ) Value.

The time series data separator 130 separates the data used for calculating the final prediction data from the evaluation data used for evaluation of the final prediction data from the input time series data. According to this configuration, it is possible to perform prediction of a future time point as well as estimation of a prediction result using input time series data.

The forward directional arithmetic analysis model building unit 140 constructs a forward directional arithmetic analysis model using the time series data, and the first prediction data calculation unit 150 uses the forward directional arithmetic analysis model to calculate first predicted data for the future .

Forward ARIMA means performing ARIMA analysis in the order of time from the past to the future when performing time series analysis in the same way as in the past. The ARIMA model is largely estimated through four steps: Identification of the model, Estimation of the parameter, Diagnotic, and Forecasting.

Identify the characteristics of the agricultural and fisheries time series data in the identification step and select the order and the number of the differences and the periods p and q of the time series data to determine the form of the ARIMA (p, d, q) model. Before determining the number of differences, the unit root test is performed on the raw series data, and the difference is not stable.

The next step is to estimate the minimum squared estimation method, the maximum likelihood estimation method and so on, and estimate the values of AIC (Akaike Information Ciriterion) and BIC (Bayesian Information Criterion) do.

The stage of diagnosis is to determine how well the estimated time series is explained by the model and to determine the suitability of the model by residual analysis. If it does not, it returns to the identification or estimation stage, repeats the process of model estimation again, and makes the actual prediction if it is judged to be appropriate.

The reverse arithmetic model building unit 160 constructs a reverse arithmetic analysis model using the time series data in the reverse direction, and the matching data calculating unit 170 calculates the fitted data using the reverse arithmetic analysis model.

Backward ARIMA means to perform ARIMA analysis in the reverse order of time in the past in the future. If you create an ARIMA model in the reverse order of time, the past predictions of the model will eventually become the future predictors of the original series data. In other words, the backward ARIMA performs the same ARIMA analysis procedure with the original series data in the reverse direction.

However, the backward ARIMA model predicts the past of the original series data, but the future of the original series data is difficult to predict because it is the past forecast in the reverse order of time data.

Accordingly, the proximity prediction model construction unit 180 constructs a proximity prediction model using the nonparametric analysis method using the fitness data in the opposite direction, and the second prediction data calculation unit 190 calculates the proximity prediction model And calculates second prediction data for the time.

In other words, we use ARIMA Fitted data (ARIMA Fitted data) in the backward ARIMA model to perform past predictions (ie, future predictions of source series data) Make predictions.

LOESS predicts the backward ARIMA model with the learned data to best fit the trend of the backward model. A non-parametric regression analysis, LOESS, allows us to predict past backward ARIMA models. At this time, the purpose of the backward ARIMA analysis is to influence the backward ARIMA model against the forward ARIMA prediction.

The final prediction data calculation unit 200 calculates the final prediction data by combining the first prediction data and the second prediction data. At this time, the final prediction data can be calculated using the weighted average of the first prediction data and the second prediction data.

This arrangement allows the forward ARIMA model to be influenced by future forecasts of the ARIMA model in the reverse order of time so that even if there is a sudden change in factors such as weather, The prediction of the model can follow the actual change quickly and increase the predictive power. An example of a Forward-Backward Loess algorithm is as follows.

The prediction data evaluating unit 210 evaluates final prediction data, and the parameter changing unit 220 changes a smoothing parameter of the local weighted polynomial analysis model when the final prediction data is out of a preset evaluation reference. According to this configuration, the setting of the prediction model can be adjusted in accordance with the prediction result to construct an optimum prediction model.

At this time, the prediction data evaluation unit 220 can compare the final prediction data with the first prediction data, and compare the final prediction data calculated using different smoothing parameters with each other.

For example, the parameter α (span) of the LOESS model is set at (λ + 1) / n <α <1 (λ: polynomial degree, n: whole observations) You can set the value that brings about the predictive power or you can decide by the user's experience. For example, if you are making a daily forecast of agricultural and fishery products, you can set α based on your experience that close-in-the-past data about 1-2 weeks is important.

FIG. 2 is a schematic flowchart of a time series prediction method performed by the system of FIG. 1, and FIG. 3 is a more specific flowchart of FIG.

2 and 3, the time series system first receives time series data (S100), and performs preprocessing on the input time series data (S110). To this end, an abnormal value is detected and substituted in the inputted time series data (S112), and the train data (Train data) used for calculating the final prediction data and the test data (test data) used for evaluation of the final prediction data are separated (114). Spline analysis methods are preferred for outlier detection and missing value processing, but other alternative analytical methods are also possible.

4 is a graph showing an example of replacing an ideal value due to an input error with a spline value. 4, an abnormal value is shown at the upper end of FIG. 4. However, it can be confirmed at the lower end of FIG. 4 that a value greater than a specific value is replaced with a spline value by spline analysis.

In addition, the length of the train data can be preset by a user or the like, and can be determined to be about 2/3 or 3/4 of the entire time series data, for example.

Next, the forward directional arithmetic analysis is performed using time series data to generate predictive data (S120). More specifically, an ARIMA analysis model is constructed with train time series data (S122), predicts n future data (S124), stores forward directional predictive data (S126) The predicted value (MSE) of the forward arithmetic prediction and the test data is stored (S128). FIG. 5 is a graph illustrating an example in which a Forward ARIMA analysis is performed and 5 days are predicted. A plot showing the fit values together with the raw diagram after forward arithmetic analysis is shown.

Next, reverse arithmetic analysis is performed using time series data (S130) to generate backward compatibility prediction data (S140). More specifically, after taking an inverse of the train time series data, the arithmetic analysis model is constructed (Backward ARIMA) (S132), and the fitted data of the Arima model is taken again in the reverse direction (S134) And generates Reversed fitted data (S140).

FIG. 6 is a graph showing an example in which backward ARIMA analysis is performed in the reverse direction of time, and FIG. 7 is a graph illustrating an example in which relevance data learned in the model of FIG. An example of the model calculated by the reverse arithmetic analysis in FIG. 6 is as follows.

Next, the prediction of the backward ARIMA model is approximated by a non-parametric analysis method (S150). For non-parametric analysis, it is preferable to use Local Weighted Polynomial Regression (LOESS), but other methods may be used. At this time, the local data is the number of proximate data that determines a smoothing parameter.

More specifically, a 'near' value, which is the number of local data, is determined (S152), a LOESS analysis model is constructed with reversed fitted data, and n future data are predicted in the future (S154) And stores the prediction data (S156). In this case, the parameter α (span) can be determined by repeatedly performing the LOESS analysis on the learned prediction data of the backward ARIMA model.

The parameter a (span) can be expressed as:

α (span) = near (number of local data) / all data (number of total data)

This means that the near value can be expressed as a product of α (span) and total data. Therefore, instead of inputting the parameter α (span), LOESS analysis can be repeated using different near values. FIG. 8 is a graph showing a result of repeatedly performing LOESS analysis using different parameters a (span).

Next, the final predicted value is obtained by applying a weight to each of the predicted value of the forward-directional ARIMA model and the backward-directional ARAMA LOESS predicted value (S160). At this time, the weight value can use a simple average or various other ensemble techniques.

Finally, the final prediction data is evaluated (S170), and the final estimation data that has been evaluated is output (S180). For the evaluation, we can compare the MSE values obtained by predicting 5 days after the FBIOESS analysis for the same interval as the MSE value obtained by the 5-day forecast after performing the conventional simple ARIMA analysis.

In the present invention, a model for short-term prediction of auction prices of agricultural and marine products through time series analysis is proposed. Algorithm that further improves predictive power by integrating Forward ARIMA model and Backward ARIMA model in ARIMA model which is the most widely used analytical model for existing time series forecast and suitable for agricultural and marine auction price data .

If the forecast of agricultural and marine product prices is made by the ARIMA analysis, the predicted value often shows a time difference, and the pattern of the observed change is late. Therefore, the forecasted level is often low. In the present invention, ARIMA Forward-Backward Loess Algorithm for Forward and Backward.

The basic idea of this model is to add the influence of the future prediction of the ARIMA model in the reverse order of time in the existing ARIMA model to compensate for the later predicted problem and expect better prediction results. In other words, we build a reverse ARIMA model and use it to predict future values, rather than simply use it to predict past values. To do this, we predict the future predictions of the ARIMA model in the reverse order of the predicted value and time in the existing ARIMA model by ensemble.

The time series analysis through the present invention solves the problem of the late prediction, which is a problem of the conventional ARIMA time series analysis, and shows a further improved prediction ability from the fluctuating data. The present invention can be applied to any industry in which daily data, such as agricultural and aquatic products auction prices, or daily or hourly data or time series analysis of big data are required. Especially useful for short-term prediction.

Although the present invention has been described in terms of some preferred embodiments, the scope of the present invention should not be limited thereby but should be modified and improved in accordance with the above-described embodiments.

100: Time Series Prediction System
110: Time series data input unit
120: time series data preprocessing section
130: Time series data separator
140: Forward Arima analysis model construction part
150: first prediction data calculation unit
160: Reverse arima model construction part
170: Adaptation data calculation unit
180: Proximity prediction model construction unit
190: second prediction data calculation unit
200: final prediction data calculation unit
210: prediction data evaluation unit
220: Parameter changing section

Claims

A time series data input unit for receiving time series data;
An arithmetic analysis model building unit for constructing a forward directional arithmetic analysis model using the time series data;
A first predictive data calculation unit for calculating first predictive data for a future time point set in advance using the forward-directional arithmetic analysis model;
A reverse arithmetic model building unit for constructing a reverse arithmetic analysis model using the time series data in a reverse direction;
A learning data calculating unit for calculating fitted data using the backward arithmetic analysis model;
A proximity prediction model building unit for performing a past prediction of the backward Arima analysis model using the learning result data in a backward direction and constructing a proximity prediction model using a nonparametric analysis method;
A second prediction data calculation unit for calculating second prediction data for the preset future time point using the proximity prediction model; And
And a final prediction data calculation unit for calculating final prediction data by combining the first prediction data and the second prediction data,
Wherein the proximity prediction model using the non-parametric analysis method is a locally weighted polynomial regression (LOESS) analysis model.

delete

The method according to claim 1,
Wherein the final prediction data is calculated using a weighted average of the first prediction data and the second prediction data.

The method according to claim 1,
A prediction data evaluation unit for evaluating the final prediction data; And
And a smoothing parameter changing unit for changing a smoothing parameter of the local weighted polynomial analysis model when the final prediction data is out of a predetermined evaluation criterion.

5. The method of claim 4,
Wherein the prediction data evaluating unit comprises:
And compares the final prediction data with the first prediction data.

5. The method of claim 4,
Wherein the prediction data evaluating unit comprises:
And compares the final prediction data calculated using different smoothing parameters with each other.

5. The method of claim 4,
And a time-series data separator for separating the data used for calculating the final predictive data from the time-series data and the evaluation data used for evaluation of the final predictive data.

The method according to claim 1,
And a time series data preprocessing unit for detecting and replacing an abnormal value in the input time series data.

The time-
A time series data input step of receiving time series data;
Constructing a forward directional arithmetic analysis model using the time series data;
A first predicted data calculation step of calculating first predicted data for a future time point set in advance using the forward directional arithmetic analysis model;
A reverse arithmetic analysis model building step of constructing a reverse arithmetic analysis model using the time series data in a reverse direction;
A learning data calculating step of calculating the fitted data using the reverse arithmetic analysis model;
A neighboring prediction model building step of performing a past prediction of the reverse arithmetic analysis model using the learning result data in a reverse direction and constructing a proximity prediction model using a non-parametric analysis method;
A second predicted data calculation step of calculating second predicted data for the future future time point using the proximity prediction model; And
And a final prediction data calculation step of calculating final prediction data by combining the first prediction data and the second prediction data,
Wherein the proximity prediction model using the non-parametric analysis method is a locally weighted polynomial regression (LOESS) analysis model.

delete

10. The method of claim 9,
Wherein the final prediction data is calculated using a weighted average of the first prediction data and the second prediction data.

10. The method of claim 9,
A prediction data evaluation step of evaluating the final prediction data; And
And a smoothing parameter changing step of changing a smoothing parameter of the local weighted polynomial analysis model when the final prediction data is out of a predetermined evaluation criterion.

13. The method of claim 12,
Wherein the prediction data evaluation step comprises:
And comparing the final prediction data with the first prediction data.

13. The method of claim 12,
Wherein the prediction data evaluation step comprises:
And comparing the calculated final prediction data using different smoothing parameters.

13. The method of claim 12,
And separating the data used for calculating the final prediction data from the evaluation data used for evaluation of the final prediction data from the time series data.

10. The method of claim 9,
Further comprising a time series data preprocessing step of detecting and replacing an abnormal value in the input time series data.

A recording medium on which a computer-readable program for executing the method according to any one of claims 9 to 11 is recorded.