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本文应用余弦模型分析法与圆形分布构成比法探讨蓬溪县１９５０～１９９１年麻疹发病季节特征。求得平均角α为８６．９８°，发病高峰时点相当于４月１１日，高峰时区为１月１３日～７月１０日。求得简单余弦曲线方程为：Ｙ１ｉ＝１．０９６＋０．２６３Ｃｏｓ（ｔｉ－８６．２９°），含第二谐量三角多项式为：Ｙ２ｉ＝１．０９６＋０．２６３Ｃｏｓ（ｔｉ－８６．２９°）＋０．０４５Ｃｏｓ（２ｔｉ－１８２．５５°）。求得决定系数Ｒ２１＝＝０．９４，Ｒ２２＝０．９９，表明用简单余弦模型拟合可使麻疹发病率Ｙｉ的变异减少９４％，用含第二谐量三角多项式拟合可使Ｙｉ的变异减少９９％。
In this paper, the seasonal characteristics of the incidence of measles from 1950 to 1991 in Pengxi County were investigated by cosine model analysis and circular distribution ratio method. The average angle α was found to be 86.98 °. The peak incidence was equivalent to April 11 and the peak time zone was January 13 to July 10. The simple cosine curve equation is obtained as follows: Y1i = 1.096 + 0.263Cos (ti-86.29 °), with the second harmonic trigonometric polynomial: Y2i = 1.096 + 0.263Cos (ti-86.29 °) +0. 045Cos (2ti-182.55 °). The determination coefficients R21 == 0.94 and R22 = 0.99 were obtained, indicating that the variation of measles incidence Yi can be reduced by 94% with the simple cosine model fitting. Using the second harmonic triangle polynomial fitting, Yi Variation is reduced by 99%.