Refers to the AutoRegressive Integrated Moving Average model used in time series modeling both for data description and for forecasting. This model generalizes the ARMA model by including a term for differencing, which is useful for removing trends and handling some types of non-stationarity.

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29 views

Why only full ARIMA models in auto.arima?

It seems that the auto.arima() function in the forecast package in R only considers full ...
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1answer
35 views

Peak Hours for Tweeting

I am trying to figure out the peak hours during a 24 hour period for my companies twitter account. We are trying to find the sweet spot to optimize our interactions (RT+Replies+Favorites). I have ...
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19 views

Statistical test: Does actual time series data deviate from forecast?

I have made a prediction of future sales based on an ARIMA model. The ARIMA model is based on past data, during which there has been no marketing activity. During the period predicted by ARIMA, I will ...
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30 views

“Frequency” value for seconds/minutes intervals data in R

I'm using R(3.1.1), and ARIMA models for forecasting. I would like to know what should be the "frequency" parameter, which is assigned in the ts() function, if im ...
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14 views

Auto.arima choose between lots of regressors

I have to forecast data with two seasonality with ARIMA. I find that I have to use a code like this: ...
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1answer
68 views

ARIMAX with a specified nonlinear model using the arima function in R

I am interested in fitting an ARIMAX model using R. As known, ARIMAX can be understood as a composition of ARIMA models and regression models with exogenous (independent) variables. I have a time ...
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2answers
48 views

Time series with autoregressive error

How can I in R fit a time series, $x_t$, with external regressors, $v_t$, and an autoregressive error? This time series model is given as follows, $x_t = \beta v_t + \epsilon_t$ where $\epsilon_t = ...
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1answer
31 views

Multivariate Time Series Forecasting in R - data in 10 minute intervals

I have data where an observation was made in 10 minute intervals for 8 weeks. I have around 170 variables that were measured every 10 minutes. I am trying to use multivariate time series analysis to ...
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36 views

what is 1-step ahead prediction for this AR(2) model?

AR(2) model : rt= 1.2rt-1 - 0.35 rt-2 +at, Var(at)=16 Suppose that r300 = 7, r299=5, and r298=6 What is the 1-step ahead prediction of r301 at the forecast origin T=300? Compute the variance of ...
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1answer
58 views

how to use arima to do mean model

I am learning arima by this site: http://people.duke.edu/~rnau/411home.htm and I want to get the same result as following notes: ...
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13 views

Using SAR and SMA in the same regression

From this webpage: http://people.duke.edu/~rnau/arimrule.htm, of the Duke University: Rule 13: If the autocorrelation at the seasonal period is positive, consider adding an SAR term to the model. ...
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2answers
138 views

very high frequency time series analysis (seconds) and Forecasting (Python/R)

I have high frequency data (observations separated by seconds), which I'd like to analyse and eventually forecast short-term periods (1/5/10/15/60 min ahead) using ARIMA models. My whole data set is ...
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20 views

Parameter estimation for dynamic regression models with correlated noise ARMA errors

I'm reading the Dynamic Regression Models chapter ( https://www.otexts.org/fpp/9/1 ) in Professor Hyndman's book, and I couldn't understand how to fit the regression model when the error is modeled ...
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2answers
71 views

Seasonal adjustment for a series that has already been adjusted

A dataset I am working with (from the OECD), for harmonised unemployment seems to be seasonally adjusted: The unemployment rates shown here are calculated as the number of unemployed persons as a ...
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1answer
26 views

My transfer function has non-stationary inputs, but a stationary output. Should I difference both the inputs and outputs during structure estimation?

I have a system of two inputs and one output that I'd like to model using the following Box-Jenkins transfer function ("dynamic regression") structure: $$y_t=\frac ...
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94 views

Obtaining the SarimaX equation from the arima coefficients

I have a SarimaX model with three regressor variables: ...
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1answer
22 views

Number of inputs used by ARIMA model

Should be an easy question but Google failed me. When using ANN for series forecasting one often uses may variables. For instance the number of shoppers might be determined by the previous number of ...
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72 views

Stock closing price forecasting using ARIMA model in R

I have downloaded the daily stock Adjusted Close price of one stock from sep 2011 to till date. As per my study plan, I have plotted some basic plots to understand the daily stock Adjusted closing ...
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2answers
46 views

Problem in ARIMA Model in R

I am running ARIMA model in R and I used auto.arima(X) function to decide appropriate model.After using this function I found that the order of my model is ARIMA(2,1,0). The problem is I run the same ...
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1answer
53 views

Difference between the forecast and simulate functions in the {forecast} package in R

I have been using the forecast package in R to make forecasts based on an ARIMA model and have noticed a difference in the output of the forecast and simulate functions when calculating confidence ...
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1answer
117 views

Forecasting a seasonal time series in R

Forecasting airline passengers seasonal time series using auto arima Hi, I am trying to model some airline data in an attempt to provide an accurate monthly forecast for June-December this year using ...
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34 views

Creating auto arima for two following time series with two different non linear slopes

I'm trying to model (and predict) the following time series, which consist of two periods (enrollment period and non enrollment) as the following: I believe that this model should consist of two ...
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42 views

Fitting ARIMAX with lagged X variable (Matlab)

This question is divided into two parts. I currently have a Y vector with 364 data points (Y) and an exogenous variable (X) with 364 data point. X is a good predictor for Y that I want to pair up ...
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35 views

ARIMAX model or ARDL?

I would like to study the impact the advertising of a product on its sales (weekly data for 5 years). As the final aim is to forecast what would be the impact on sales of a change in the advertising ...
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2answers
35 views

How to compare AR and ARIMA models?

Relatively new to stats. I use linear regression and get R^2, which is quite low. MODEL 1 lmoutar=lm(formula = ts_y ~ ts_y_lag + ts_x) So switched to arima ...
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13 views

Question of Holt-Winters, parameter chosen

I am using Holt-Winters to do a time-series forecasting. The package chose gamma equal to 1 for me. I am wondering what that means. The prediction works pretty well overall. When will you use this ...
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28 views

What is the equation for an ARIMA (2,1,0)?

Trying to figure out how JMP calculates its results. Seems the differencing equation does not produce same result as JMP. ...
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1answer
62 views

Forecasting at individual versus grouped level

I have monthly usage data (spanning 3 years) for a customer base of around 200K, and I need to generate 1-month ahead forecasts for each of them. There are a couple of exogenous variables that would ...
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29 views

Statistical demand forecasting

How is batch demand forecasting done in retail like in Walmart where number of products to forecast are very large in number and products are short lived i.e have less than 36 months of historical ...
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35 views

Arima model for non-negative data

I have been reading a tutorial for an introduction to time series. It contains a dataset, with an $Arima(2,0,0)$ forecast along with a 80% and 95% prediction interval. It looks like this: This ...
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20 views

How to get observations from residuals in an ARIMA model?

If we have residuals of an ARIMA(p,d,q) with known parameters, how can we retrieve the original observations of the time series?
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37 views

Reproducing ARIMA error terms

When forecasting a moving average (MA) model using R's forecast, why does using residuals(fit) produce different results than ...
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22 views

How do I determine the innovation term in an ARIMA equation?

I am not a statistics specialist : I had to take over the internship subject of another student to include it in mine. He was working with $SARIMAX$ models and I would like to import them in an ...
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38 views

Interpretation of the partial autocorrelation function for a pure MA process

I have been working with some time-series theory and I noticed something that I can understand "mathematically", but not based on the intuitive explanations of what the partial auto-correlation ...
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1answer
35 views

Seasonal vs non-seasonal coefficients in R ARIMA

Let's say I have the two following ARIMA models: ARIMA(7,1,1) (no seasonality) ARIMA(6,1,1)(1,0,0)7 (seasonality of period 7). Are they conceptually the same? If so, why is that when I model ...
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24 views

Why is $R^2$ poor for AR model selection used for forecasting?

There is a related question here, about how to calculate the R-squared on a regression with ARIMA errors. I found the answer quite useful, and hoped for some elaboration, particularly on Rob's closing ...
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1answer
51 views

Why we check the residuals of ARIMA model for white Gaussian?

I have problem about the assumptions and model verification of ARIMA models. I know that Gaussian distributed assumption is not necessary for fitting ARIMA models but I wonder why a lot of people ...
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28 views

Autoregressive model with input variables in proc arima procedure

I am currently working on the time series analysis for series Y but I have to use other two variable A and B as an input variable in SAS proc arima procedure. But I am unable to interpret the cross ...
2
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1answer
67 views

time-series analysis Vs statistical signal processing

Is there a way to identify when to use time series analysis or signal processing. Time series data analysis can be divided to signal processing and normal time series analysis. In signal processing ...
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41 views

Estimating error in ARIMA(p,d,q)

I am trying to model my data with ARIMA(1,2,12) and since the variance is not stationary I have also included GARCH (2,3). I have saved all the parameter of my model in a variable called mdl. I have ...
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0answers
24 views

How do I calculate the standard error of the ACF if the errors are t-distributed?

I am modeling my data with ARIMA and to check if my model is good I have to compute the residuals and plot the correlation function and partial correlation function of the residuals. If the results of ...
2
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1answer
109 views

R: forecast function accuracy for ARIMA models

I have a problem with the forecast function for ARIMA models in R. It calls predict that calls ...
4
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1answer
67 views

Sample Mean of AR(1) model

Consider the AR(1) model with iid innovations with finite mean and variance. Also, let $X_0 = 0$. \begin{align} X_t = \phi X_{t-1} + \epsilon_t \end{align} The goal is to derive the asymptotic ...
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23 views

Retreiving Integrated Fitted Data from Stationary Fitted Data

Note that this is a simplified example: I have some time series that I made stationary by differencing twice. Then I ran arima on it, and set d = 0 to prevent ...
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2answers
89 views

Arima with xreg, rebuilding the fitted values by hand

I'm using R to do some time series estimation. I'm trying to rebuild the fitted values from an Arima model by hand to use in an Excel spreadsheet using the estimated coefficients and the input data. ...
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0answers
12 views

What are the benefits of normality assumption for AR(I)MA models?

I know normality assumption is not necessary for all of the ARIMA models. My question is that if we have a non-normal time series, is it better to transform it to normal state by transformations like ...
4
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0answers
49 views

Determining parameters in AR model for non-stationary time series

I am currently trying to fit an AR model to some financial data. The time series $Y_t$ in levels is clearly non-stationary; however it appears the first differences $dY_t$ are stationary (and this is ...
0
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1answer
89 views

ARIMA, adjustments and intervention analysis

I have very little knowledge of time-series analysis (despite my stat master - didn't do anything else than an introductory course) but now I'm facing a statistical problem whose answer is this very ...
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73 views

Arima function doesn't consider seasonal components

Currently trying to fit several models to some data sets in order to find an accurate enough one, I ran into some difficulties with the Arima function of the ...
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0answers
38 views

VARMAX model in R

Is there a function in R that estimates the VARMAX model? There is one for a VARX (MTS package), but I didn't find one that works with the MA part also...