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概率和统计延伸

社交网络建模

偏移 Gompertz 分布是按独立指数和极值分布的随机变量的最大值的分布. 该分布可用于模拟社交网络关注的增长和下降. 以下为偏移 Gompertz 分布的 CDF 形式.

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CDF[ShiftedGompertzDistribution[\[Lambda], \[Xi]], x]
Out[1]=

谷歌趋势(Google trends)的 Facebook 中的每周关注计数.

In[2]:=
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ts = TemporalData[TimeSeries, {CompressedData[" 1:eJyFz2tPwjAUBmDA+7wRNCpeQBTRiAGvXLoNYYytPW03QHSybiYav/tX/Ume GRO/mPg0p+l72pykpbeP8VsmlUqlsT5xS/8n82smM/Nt9sdcYv4vC2gxoWlL mqYto5WVVbS2tp7N5nK5jY3N7Z2tnXx+d3dvbx/XQbFwUCgUi4eHpdLRcbl8 UjmtnJ1XqxeoVqvV65dX9cvrZvP2pnHXaLUbjWaLIJMYuk4MwzTNTue+1+1a qO9a9qA/cPq2PRg4ILnLgHPGgLkuABfSdRyHUs5AAghvyD3peb4U+IhLJoCB NxLUk0JwgXcCRNIT2AYpPS4YByo5cGBsFL+oOFaRCqP4/VWpOFQqCKbhVEXh 9BmFKopjTFEQBs9PweRxNHkYj/yh7/ueEHI8xDGAg7AAqMsodRw3OTP2HWxK XfyFbVl2z+p2kGn1jATRSZsQXW+RNkpSmxjkC/7xXxc= "], { TemporalData`DateSpecification[{2006, 8, 26, 0, 0, 0.}, { 2015, 7, 11, 0, 0, 0.}, {1, "Week"}]}, 1, {"Continuous", 1}, { "Discrete", 1}, 1, { ValueDimensions -> 1, DateFunction -> Automatic, ResamplingMethod -> {"Interpolation", InterpolationOrder -> 1}}}, True, 314.1];
显示完整的 Wolfram 语言输入
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DateListPlot[ts, ImageSize -> Medium, PlotTheme -> "Detailed", Filling -> Axis]
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用截断偏移 Gompertz 分布拟合数据.

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rawcounts = ts["Values"]; length = Length[rawcounts]; x = Range[length] - 0.5; wdata = WeightedData[x, rawcounts];
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edist = EstimatedDistribution[wdata, TruncatedDistribution[{0, length}, ShiftedGompertzDistribution[\[Lambda], \[Xi]]], {{\[Lambda], 1}, {\[Xi], 6}}]
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比较模型预测和数据.

显示完整的 Wolfram 语言输入
In[6]:=
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counts = Total[rawcounts] PDF[edist , x]; DateListPlot[{rawcounts, counts}, {ts["FirstDate"], Automatic, "Week"}, Filling -> Axis, PlotLegends -> {"data", "model"}, ImageSize -> Medium, PlotTheme -> "Detailed"]
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