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All Journal Jurnal Matematika: MANTIK Parameter: Jurnal Matematika, Statistika dan Terapannya
Muhammad Fajar
Badan Pusat Statistik, Indonesia
Mathematics

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Modeling of COVID-19 Epidemic Growth Curve in Indonesia Muhammad Fajar; Wahyudi Wahyudi
Jurnal Matematika MANTIK Vol. 7 No. 1 (2021): Mathematics and Applied Mathematics
Publisher : Mathematics Department, Faculty of Science and Technology, UIN Sunan Ampel Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15642/mantik.2021.7.1.67-73

Abstract

Aim of this study is to make parametric modeling of the COVID-19 epidemic growth curve so that the maximum value and time at that point can be obtained from the cumulative cases of COVID-19. The data used in this study is the cumulative number of positive confirmed cases of COVID-19 from https://covid19.go.id/. The method used in this study is fitting data with the Logistic and Gompertz models. Result of this study are (1) the Logistic and Gompertz models are very fit in modeling the COVID-19 epidemic growth curve, indicated from the value of R2 (coefficient of determination) which reaches more than 99%; (2) From the Logistics model it is obtained that the estimated amount of the maximum cumulative case at the end of the COVID-19 epidemic is 7,714 positive confirmed cases, achieved in about 82 days (May 22, 2020) from Mar 2, 2020, when the first positive COVID-19 case was announced by the government; and (3) From the Gompertz model, it is obtained that the estimated maximum cumulative case at the end of the COVID-19 epidemic is 33,975 positive confirmed cases, achieved in about 152 days (Jul 30, 2020) from Mar 2, 2020. The results of this study can be used as input to the government to take steps in controlling the spread of COVID-19.
The Testing of Existence Wagner's Law in Papua Province Muhammad Fajar; Yuyun Guna Winarti
Jurnal Matematika MANTIK Vol. 7 No. 2 (2021): Mathematics and Applied Mathematics
Publisher : Mathematics Department, Faculty of Science and Technology, UIN Sunan Ampel Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15642/mantik.2021.7.2.132-139

Abstract

The Law of Wagner is supposedly not universally applicable. There are debates about the truth of this law. Based on this phenomenon, the purpose of this study is to examine the existence of Wagner's Law in the economy of Papua Province. Data used in this research are GRDP (Gross Regional Domestic Product) at the constant price (Real GRDP) and government expenditure at the constant price (Real GOV) in the form of natural logarithms (the base year 2000) from all municipalities in Papua Province from 2000 to 2013. Data source comes from Badan Pusat Statistik-Statistics Indonesia. The method used in this research is The Kao Cointegration Test and The Granger Causality Test. These methods indicate the possibility of short-term and long-term effects across economic variables. The result of this study concludes that there is a significant relationship between government expenditure and Gross Regional Domestic Product (GRDP). This result means that Wagner’s Law is not proven in the Papuan economy. This is supported by a causality test which shows government expenditure is granger cause of the real GDP, but not vice versa. However, the two variables are cointegrating.
Forecasting Regional Economic Growth Using TVARX: Model Accuracy Evaluation in Banten Province Amelia Vega; Muhammad Fajar; Hendro Prayitno; Erya Afrianus
Parameter: Jurnal Matematika, Statistika dan Terapannya Vol 4 No 3 (2025): Parameter: Jurnal Matematika, Statistika dan Terapannya
Publisher : Jurusan Matematika FMIPA Universitas Pattimura

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30598/parameterv4i3pp551-562

Abstract

Forecasting regional economic performance is essential for supporting timely and responsive policy planning. This study aims to forecast the Gross Regional Domestic Product at constant prices (GRDP) in Banten Province for the second to fourth quarters of 2025 using the Time-Varying Autoregressive model with Exogenous Variables (TVARX). The model incorporates household final consumption expenditure, gross fixed capital formation, exchange rates, and export values as exogenous variables. Model performance was evaluated by comparing combinations of training-testing data proportions (90:10, 80:20, 70:30, and 60:40) and two estimation approaches (local constant and local linear), using the Mean Absolute Percentage Error (MAPE) as the predictive accuracy metric. All variables were transformed into logarithmic form and differenced to ensure stationarity. The results indicate that the model using a 90:10 data split and the local linear estimation approach yielded the most accurate prediction, with the lowest MAPE value of 0.6%. The best-performing model was then applied to forecast out-of-sample GRDP CP for the next three quarters, with its year-on-year growth subsequently analyzed. These findings are expected to serve as a basis for data-driven economic analysis and support macroeconomic planning that is responsive to short-term structural dynamics.
Co-Authors Amelia Vega Erya Afrianus Hendro Prayitno Wahyudi Wahyudi Yuyun Guna Winarti