Online Bayesian Time-varying Parameter Estimation of HIV-1 Time-series*

Structural Breaks and Instability of Money Demand in IndonesiaThis research aims to identify the sources of instability of the money demand function (M1 and M2) due to structural changes that occur as a result of economic shocks. These shocks, are technically shown by the presence of structural breaks in the data and can lead the parameters non-constancy. The instability of the money demand function was analyzed using the Gregory and Hansen test. The source of instability of the money demand was identified using time varying parameter model. This research used quarterly time series data from 1993Q1 to 2013Q4. The result of Gregory and Hansen test indicates there is no long term equilibrium between variables (money demand, income, domestic interest rate, foreign interest rate, exchange rate, and inflation) in the model, neither M1 nor M2 model. On the other word, money demand function is unstable. The source of the instability is exchange rate variable.Keywords: Stability Money Demand; Structural Breaks; Time Varying Parameter ModelAbstrakPenelitian ini bertujuan untuk mengidentifikasi sumber-sumber ketidakstabilan fungsi permintaan uang (M1 dan M2) akibat dari perubahan struktural yang terjadi karena adanya guncangan ekonomi. Guncangan tersebut, yang secara teknis ditunjukkan oleh keberadaan structural breaks di dalam data, dapat menyebabkan parameter menjadi tidak konstan. Ketidakstabilan fungsi permintaan uang dianalisis dengan menggunakan Gregory and Hansen test. Sumber ketidakstabilan dari permintaan uang diidentifikasi dengan menggunakan time varying parameter model. Penelitian ini menggunakan data time series dalam bentuk kuartalan dari 1993Q1 sampai 2013Q4. Hasil Gregory and Hansen test menunjukkan bahwa tidak ada keseimbangan jangka panjang di antara variabel-variabel (permintaan uang, pendapatan, suku bunga domestik, suku bunga luar negeri, nilai tukar, dan inflasi) di dalam model, baik pada model M1 maupun M2. Dengan kata lain, fungsi permintaan uang tidak stabil. Sumber ketidakstabilan tersebut berasal dari variabel nilai tukar.

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Hydrological model performance and parameter estimation in the wavelet-domain

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-6-2451-2009 ◽

2009 ◽

Vol 6 (2) ◽

pp. 2451-2498 ◽

Cited By ~ 4

Author(s):

B. Schaefli ◽

E. Zehe

Keyword(s):

Time Series ◽

Parameter Estimation ◽

Time Domain ◽

Model Performance ◽

Time Varying ◽

Wavelet Domain ◽

Frequency Content ◽

Time Varying Frequency ◽

The Time Domain

Abstract. This paper proposes a method for rainfall-runoff model calibration and performance analysis in the wavelet-domain by fitting the estimated wavelet-power spectrum (a representation of the time-varying frequency content of a time series) of a simulated discharge series to the one of the corresponding observed time series. As discussed in this paper, calibrating hydrological models so as to reproduce the time-varying frequency content of the observed signal can lead to different results than parameter estimation in the time-domain. Therefore, wavelet-domain parameter estimation has the potential to give new insights into model performance and to reveal model structural deficiencies. We apply the proposed method to synthetic case studies and a real-world discharge modeling case study and discuss how model diagnosis can benefit from an analysis in the wavelet-domain. The results show that for the real-world case study of precipitation – runoff modeling for a high alpine catchment, the calibrated discharge simulation captures the dynamics of the observed time series better than the results obtained through calibration in the time-domain. In addition, the wavelet-domain performance assessment of this case study highlights which frequencies are not well reproduced by the model, which gives specific indications about how to improve the model structure.

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