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Introducción a Series de Tiempo Univariadas - Centro Microdatos

Introducción a Series de Tiempo Univariadas - Centro Microdatos

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Introducción a <strong>Series</strong> <strong>de</strong> <strong>Tiempo</strong> <strong>Univariadas</strong>December 31, 2010IV.5 Filtro Holt-WintersIV.5.1 Sin estacionalidadEl método <strong>de</strong> suavización exponencial doble, utilizaba el mismo parámetro , en las dossuavizaciones realizadas a la serie. El método Holt-Winters libera este supuesto permitiendo queel parámetro <strong>de</strong> suavización <strong>de</strong>l primer filtro sea diferente al <strong>de</strong>l segundo.La sintaxis <strong>de</strong>l comando STATA para realizar este filtro es:tssmooth hwinters [type] newvar = exp [if] [in] [, options]Con las mismas opciones <strong>de</strong> los comandos anteriores.Veamos que resulta <strong>de</strong> utilizar el filtro Holt-Winters en la serie <strong>de</strong> tiempo cosecha <strong>de</strong> salmónatlántico.use sa, cleartsset fechatime variable: fecha, 2000m1 to 2010m8<strong>de</strong>lta: 1 monthtssmooth hwinters sa_s1=sa, samp0(30)computing optimal weightsIteration 0:Iteration 1:Iteration 2:Iteration 3:Iteration 4:Iteration 5:Iteration 6:penalized RSS = -3.740e+09 (not concave)penalized RSS = -2.703e+09penalized RSS = -2.639e+09penalized RSS = -2.638e+09penalized RSS = -2.638e+09penalized RSS = -2.638e+09penalized RSS = -2.638e+09Optimal weights:alpha = 0.8271beta = 0.0063penalized sum-of-squared residuals = 2.64e+09sum-of-squared residuals = 2.64e+09root mean squared error = 4539.824g sa_s2=F.sa_s1(1 missing value generated)tsline sa sa_s2, legend(label(1 "Observada") label(2 "Suavizada"))45

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