|
| 1 | +{ |
| 2 | + "cells": [ |
| 3 | + { |
| 4 | + "cell_type": "markdown", |
| 5 | + "metadata": {}, |
| 6 | + "source": [ |
| 7 | + "# Julia的安装\n", |
| 8 | + "Julia是一个开源的数值计算软件,由于具有JIT等特性,所以具有非常高的性能。我们可以从Julia官网:https://julialang.org 下载和安装。\n", |
| 9 | + "Julia的界面非常简单,不适合编写程序,因而我们一般通过配置Atom, sublime等编辑器写Julia程序。此外,通过安装Jupyter,再在Julia中安装IJulia也可以使用Jupyter调用Julia。安装IJulia的方法很简单,只需要在Julia的命令界面数据「Pkg.add(\"IJulia\")」即可,其中「Pkg.add()」即安装Julia扩展包的命令。\n", |
| 10 | + "为了展示方便,我们仍然推荐使用Jupyter作为学习工具。比如此文档就是使用Jupyter写作。\n", |
| 11 | + "# 使用Julia生成随机数\n", |
| 12 | + "在Julia中,可以使用rand()函数生成随机数。最基本的是生成一个在$(0,1)$区间内的均匀分布的随机数,使用此均匀分布随机数,给定任意的分布函数$F$,可以生成服从$F$的随机数。" |
| 13 | + ] |
| 14 | + }, |
| 15 | + { |
| 16 | + "cell_type": "code", |
| 17 | + "execution_count": 2, |
| 18 | + "metadata": {}, |
| 19 | + "outputs": [ |
| 20 | + { |
| 21 | + "name": "stdout", |
| 22 | + "output_type": "stream", |
| 23 | + "text": [ |
| 24 | + "一个(0,1)区间内的随机数:0.37548057506738663\n", |
| 25 | + "20个(0,1)区间内的随机数:\n", |
| 26 | + "[0.719472, 0.447485, 0.101696, 0.166868, 0.042199, 0.29615, 0.957232, 0.688239, 0.583882, 0.30275, 0.718666, 0.945527, 0.150395, 0.650269, 0.811649, 0.770101, 0.681383, 0.066861, 0.0560345, 0.760834]" |
| 27 | + ] |
| 28 | + } |
| 29 | + ], |
| 30 | + "source": [ |
| 31 | + "## 生成一个x~Uniform(0,1)\n", |
| 32 | + "x=rand()\n", |
| 33 | + "print(\"一个(0,1)区间内的随机数:\",x,\"\\n\")\n", |
| 34 | + "\n", |
| 35 | + "## 生成20个z~Uniform(0,1)\n", |
| 36 | + "z=rand(20)\n", |
| 37 | + "print(\"20个(0,1)区间内的随机数:\",\"\\n\")\n", |
| 38 | + "print(z)" |
| 39 | + ] |
| 40 | + }, |
| 41 | + { |
| 42 | + "cell_type": "markdown", |
| 43 | + "metadata": {}, |
| 44 | + "source": [ |
| 45 | + "如果我们需要生成一个服从分布函数$F: R\\rightarrow [0,1]$的随机数,那么只要首先生成一个$(0,1)$的随机数$u$,并令$x=F^{-1}(u)$,那么新生成的$x$即服从$F$的分布。比如,指数分布的分布函数为$1-e^{-\\frac{1}{b}\\cdot x}$,其中b为一个参数,因而我们可以使用$x=-b\\cdot \\ln(u)$来生成服从指数分布的随机数。" |
| 46 | + ] |
| 47 | + }, |
| 48 | + { |
| 49 | + "cell_type": "code", |
| 50 | + "execution_count": 5, |
| 51 | + "metadata": { |
| 52 | + "scrolled": true |
| 53 | + }, |
| 54 | + "outputs": [ |
| 55 | + { |
| 56 | + "name": "stdout", |
| 57 | + "output_type": "stream", |
| 58 | + "text": [ |
| 59 | + "20个服从指数分布F(x)=1-exp{-(1/b)*x}的随机数:\n", |
| 60 | + "[2.58645, 11.1848, 0.918512, 0.543136, 3.53971, 0.259657, 1.99849, 0.350091, 3.09114, 0.165935, 0.0657694, 0.949447, 9.25605, 0.393429, 10.0648, 1.87895, 2.65323, 6.0845, 6.48842, 2.73542]" |
| 61 | + ] |
| 62 | + } |
| 63 | + ], |
| 64 | + "source": [ |
| 65 | + "## 设定参数\n", |
| 66 | + "b=3\n", |
| 67 | + "\n", |
| 68 | + "## 生成20个x~F(x)=1-exp{-(1/b)*x}\n", |
| 69 | + "x=-1*log.(rand(20))*b\n", |
| 70 | + "print(\"20个服从指数分布F(x)=1-exp{-(1/b)*x}的随机数:\\n\")\n", |
| 71 | + "print(x)" |
| 72 | + ] |
| 73 | + }, |
| 74 | + { |
| 75 | + "cell_type": "markdown", |
| 76 | + "metadata": {}, |
| 77 | + "source": [ |
| 78 | + "我们可以使用经验分布函数(Empirical distribution function)与理论的分布函数比较,来判断我们生成的随机数是否满足某一分布。经验分布函数的定义为:$\\hat{F}(x)=\\frac{1}{N}\\cdot \\sum_{i=1}^N 1\\{X_i \\leq x\\}$,也就是给定一个$x$,其经验分布函数的值为样本中小于等于$x$的比例,比如:" |
| 79 | + ] |
| 80 | + }, |
| 81 | + { |
| 82 | + "cell_type": "code", |
| 83 | + "execution_count": 20, |
| 84 | + "metadata": {}, |
| 85 | + "outputs": [ |
| 86 | + { |
| 87 | + "name": "stdout", |
| 88 | + "output_type": "stream", |
| 89 | + "text": [ |
| 90 | + " x | 分布函数 | 经验分布函数| 差的绝对值\n", |
| 91 | + "0.1 |0.0327838995179941 | 0.035 | 0.002216100482005906 \n", |
| 92 | + "0.3 |0.09516258196404037 | 0.1 | 0.004837418035959634 \n", |
| 93 | + "0.5 |0.15351827510938598 | 0.185 | 0.031481724890614016 \n", |
| 94 | + "0.7 |0.20811043366321835 | 0.255 | 0.04688956633678165 \n", |
| 95 | + "0.9 |0.2591817793182821 | 0.295 | 0.03581822068171786 \n", |
| 96 | + "1.1 |0.3069593799135585 | 0.325 | 0.018040620086441528 \n", |
| 97 | + "1.3 |0.3516556589984903 | 0.4 | 0.04834434100150975 \n", |
| 98 | + "1.5 |0.3934693402873666 | 0.455 | 0.06153065971263344 \n", |
| 99 | + "1.7 |0.43258633120299617 | 0.495 | 0.06241366879700383 \n", |
| 100 | + "1.9 |0.46918054943798604 | 0.54 | 0.070819450562014 \n", |
| 101 | + "2.1 |0.5034146962085905 | 0.575 | 0.07158530379140948 \n", |
| 102 | + "2.3 |0.5354409796390884 | 0.625 | 0.08955902036091157 \n", |
| 103 | + "2.5 |0.5654017914929217 | 0.655 | 0.08959820850707834 \n", |
| 104 | + "2.7 |0.5934303402594009 | 0.68 | 0.08656965974059916 \n", |
| 105 | + "2.9 |0.6196512434107414 | 0.715 | 0.09534875658925857 \n", |
| 106 | + "3.1 |0.6441810814626581 | 0.735 | 0.09081891853734192 \n", |
| 107 | + "3.3 |0.6671289163019204 | 0.745 | 0.0778710836980796 \n", |
| 108 | + "3.5 |0.6885967760854023 | 0.76 | 0.07140322391459775 \n", |
| 109 | + "3.7 |0.708680108866529 | 0.77 | 0.06131989113347103 \n", |
| 110 | + "3.9 |0.7274682069659874 | 0.785 | 0.05753179303401268 \n", |
| 111 | + "4.1 |0.7450446039734899 | 0.795 | 0.04995539602651011 \n", |
| 112 | + "4.3 |0.7614874461456975 | 0.8 | 0.03851255385430252 \n", |
| 113 | + "4.5 |0.7768698398515702 | 0.81 | 0.033130160148429844 \n", |
| 114 | + "4.7 |0.7912601766099203 | 0.825 | 0.03373982339007964 \n", |
| 115 | + "4.9 |0.8047224371643142 | 0.835 | 0.030277562835685723 \n", |
| 116 | + "5.1 |0.8173164759472653 | 0.845 | 0.027683524052734665 \n", |
| 117 | + "5.3 |0.8290982871984751 | 0.85 | 0.020901712801524863 \n", |
| 118 | + "5.5 |0.8401202539203061 | 0.86 | 0.019879746079693894 \n", |
| 119 | + "5.7 |0.8504313807773649 | 0.87 | 0.019568619222635086 \n", |
| 120 | + "5.9 |0.8600775119756906 | 0.87 | 0.009922488024309395 \n", |
| 121 | + "6.1 |0.8691015350902557 | 0.88 | 0.010898464909744332 \n", |
| 122 | + "6.3 |0.877543571747018 | 0.895 | 0.017456428252981993 \n", |
| 123 | + "6.5 |0.8854411560073123 | 0.895 | 0.009558843992687693 \n", |
| 124 | + "6.7 |0.8928294012476933 | 0.9 | 0.007170598752306745 \n", |
| 125 | + "6.9 |0.8997411562771962 | 0.9 | 0.0002588437228038254 \n", |
| 126 | + "7.1 |0.9062071513861237 | 0.91 | 0.0037928486138762985 \n", |
| 127 | + "7.3 |0.9122561349757057 | 0.91 | 0.002256134975705648 \n", |
| 128 | + "7.5 |0.9179150013761012 | 0.92 | 0.0020849986238988816 \n", |
| 129 | + "7.7 |0.9232089104210319 | 0.92 | 0.0032089104210318853 \n", |
| 130 | + "7.9 |0.9281613993106868 | 0.92 | 0.008161399310686712 \n", |
| 131 | + "8.1 |0.9327944872602503 | 0.925 | 0.007794487260250227 \n", |
| 132 | + "8.3 |0.9371287733993328 | 0.925 | 0.012128773399332715 \n", |
| 133 | + "8.5 |0.9411835283575701 | 0.94 | 0.001183528357570185 \n", |
| 134 | + "8.7 |0.9449767799435927 | 0.94 | 0.004976779943592802 \n", |
| 135 | + "8.9 |0.9485253932982992 | 0.945 | 0.003525393298299262 \n", |
| 136 | + "9.1 |0.9518451458788036 | 0.955 | 0.0031548541211963155 \n", |
| 137 | + "9.3 |0.9549507976064422 | 0.955 | 4.92023935577679e-5 \n", |
| 138 | + "9.5 |0.9578561564907236 | 0.955 | 0.0028561564907236825 \n", |
| 139 | + "9.7 |0.9605741400209925 | 0.96 | 0.0005741400209925418 \n", |
| 140 | + "9.9 |0.96311683259876 | 0.96 | 0.0031168325987600554 \n", |
| 141 | + "Mean absolute bias:0.03123553671578694" |
| 142 | + ] |
| 143 | + } |
| 144 | + ], |
| 145 | + "source": [ |
| 146 | + "## 设定参数\n", |
| 147 | + "b=3\n", |
| 148 | + "\n", |
| 149 | + "## 生成200个x~F(x)=1-exp{-(1/b)*x}\n", |
| 150 | + "x=-1*log.(rand(200))*b\n", |
| 151 | + "\n", |
| 152 | + "## 给定一些点,在这些点上计算分布函数和经验分布函数\n", |
| 153 | + "x_eval=[i for i in 0.1:0.2:9.9] #0.1,0.3,...,9.9\n", |
| 154 | + "\n", |
| 155 | + "## 计算理论的分布函数\n", |
| 156 | + "F=1-exp.(-1/b.*x_eval)\n", |
| 157 | + "\n", |
| 158 | + "## 给定z计算经验分布函数\n", |
| 159 | + "function empirical_F(x,z::Float64)::Float64\n", |
| 160 | + " return mean(x.<=z)\n", |
| 161 | + "end\n", |
| 162 | + "\n", |
| 163 | + "## 计算经验分布函数\n", |
| 164 | + "Fhat=[empirical_F(x,z) for z in x_eval]\n", |
| 165 | + "\n", |
| 166 | + "## 计算经验分布函数与真实的分布函数之间的绝对差异\n", |
| 167 | + "bias=mean(abs.(Fhat-F))\n", |
| 168 | + "## 打印两个分布函数及其绝对差异,以及平均的绝对差异\n", |
| 169 | + "print(\" x | 分布函数 | 经验分布函数| 差的绝对值\\n\")\n", |
| 170 | + "for i in 1:1:length(x_eval)\n", |
| 171 | + " print(\"$(x_eval[i]) |$(F[i]) | $(Fhat[i]) | $(abs(F[i]-Fhat[i])) \\n\")\n", |
| 172 | + "end\n", |
| 173 | + "print(\"Mean absolute bias:\",bias)" |
| 174 | + ] |
| 175 | + }, |
| 176 | + { |
| 177 | + "cell_type": "code", |
| 178 | + "execution_count": null, |
| 179 | + "metadata": { |
| 180 | + "collapsed": true |
| 181 | + }, |
| 182 | + "outputs": [], |
| 183 | + "source": [] |
| 184 | + } |
| 185 | + ], |
| 186 | + "metadata": { |
| 187 | + "kernelspec": { |
| 188 | + "display_name": "Julia 0.6.0", |
| 189 | + "language": "julia", |
| 190 | + "name": "julia-0.6" |
| 191 | + }, |
| 192 | + "language_info": { |
| 193 | + "file_extension": ".jl", |
| 194 | + "mimetype": "application/julia", |
| 195 | + "name": "julia", |
| 196 | + "version": "0.6.0" |
| 197 | + }, |
| 198 | + "latex_envs": { |
| 199 | + "LaTeX_envs_menu_present": true, |
| 200 | + "autocomplete": true, |
| 201 | + "bibliofile": "biblio.bib", |
| 202 | + "cite_by": "apalike", |
| 203 | + "current_citInitial": 1, |
| 204 | + "eqLabelWithNumbers": true, |
| 205 | + "eqNumInitial": 1, |
| 206 | + "hotkeys": { |
| 207 | + "equation": "Ctrl-E", |
| 208 | + "itemize": "Ctrl-I" |
| 209 | + }, |
| 210 | + "labels_anchors": false, |
| 211 | + "latex_user_defs": false, |
| 212 | + "report_style_numbering": false, |
| 213 | + "user_envs_cfg": false |
| 214 | + } |
| 215 | + }, |
| 216 | + "nbformat": 4, |
| 217 | + "nbformat_minor": 2 |
| 218 | +} |
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