X~2分布、t分布和f分布的性质及近似计算

以下为三个分布的动画演示程序，直接运行：

function dandn(action)

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%

% 《X~2分布、t分布和f分布的性质及近似计算》

%

% 制作人：幸玮石岩顾秋容

% All Rights Reserved % 2008.12

%

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%无输入参数时进行初始程序,否则调界面参数

if nargin<1,

action='initialize';

else

%看是哪种分布

data=get(gco,'UserData');

pdflabel=data(4);

%图形显示参数，调试时用

switch pdflabel

case 1

xstart=0; %x轴起始点

width=120; %x轴范围

xdis=30; %x轴刻度间距

lenth=0.24; %y轴范围

ydis=0.03; %y轴刻度间距

speed=0.6; %动画演进速率

case 2

width=6;

xdis=3;

lenth=0.42;

ydis=0.05;

speed=0.5;

case 3

width=2;

xdis=0.5;

lenth=4;

ydis=0.4;

speed=0.8;

end

end

%初始化模块

if strcmp(action,'initialize')

%数据初始化

%分布函数选择

pdflabel=0;

d=inputdlg({'输入分布函数类型:'},'选择分布函数',1,{'x2'});

if strcmp(d,'x2')

pdflabel=1;

elseif strcmp(d,'t')

pdflabel=2;

elseif strcmp(d,'f')

pdflabel=3;

end

%不符合的输入报错

if pdflabel==0

errordlg('分布函数只能选择x2,t与f')

return

end

%整体用户界面建立，图形显示窗口嵌入

figNumber=figure( ...

'Name','Changing of the X~2 destribution function', ...

'NumberTitle','off', ...

'Visible','off');

axes( ...

'Units','normalized', ...

'Visible','off', ...

'Position',[0.06 0.065 0.70 0.9]);

%显示初始现实画面

switch pdflabel

case 1

%初始显示参数

xstart=0; %x轴起始点

width=120; %x轴范围

xdis=30; %x轴刻度间距

lenth=0.24; %y轴范围

ydis=0.03; %y轴刻度间距

%画背景图

plot([xstart xstart+width],[lenth lenth],'b');

hold on

plot([xstart xstart+width],[lenth lenth],'r');

plot([xstart xstart+width],[lenth lenth],'black'); legend('X~2分布','正态分布');

axis([xstart xstart+width 0 lenth]);

grid on

set(gca,'XTick',xstart:xdis:xstart+width);

set(gca,'YTick',0:ydis:lenth);

hold off

%分布函数动画初始参数

m=0;

n=1;

case 2

width=6;

xdis=3;

lenth=0.42;

ydis=0.05;

plot([-width -width width],[0 lenth lenth],'b');

hold on

plot([-width -width width],[0 lenth lenth],'r--'); plot([-width -width width],[0 lenth lenth],'black'); legend('T分布','正态分布');

grid on

axis([-width width 0 lenth]);

set(gca,'XTick',-width:xdis:width);

set(gca,'YTick',0:ydis:lenth);

hold off

m=0;

n=2;

otherwise

width=2;

xdis=0.5;

lenth=4;

ydis=0.4;

plot(width,0,'b');

hold on

plot(width,0,'r');