clear,clc,close all;

figure('color',[1,1,1]);hold on

x = 0:0.01:5; df = [10,40;11,5];

for n = 1:length(df)

   y = fpdf(x,df(n,1),df(n,2));plot(x,y,'linewidth',1);

end

text(1.22,0.6,'$$\leftarrow n_1=10,n2=40$$','interpreter','latex');

text(2,0.19,'$$\leftarrow n_1=11,n_2=5$$','interpreter','latex');

axis([0,5,0,0.95]);grid on

%%%%%%%%%%% 上 alpha 分位数

figure('color',[1,1,1]);hold on

x = 0:0.1:5; alpha = 0.05; n1 = 5; n2= 40;

y = fpdf(x,n1,n2);plot(x,y,'linewidth',2);

fill([finv(1-alpha,n1,n2),5,5:-0.01:finv(1-alpha,n1,n2),finv(1-alpha,n1,n2),finv(1-alpha,n1,n2)],...

   [0,0,fpdf(5,n1,n2),fpdf(5:-0.01:finv(1-alpha,n1,n2),n1,n2),0],'m');

text(1,0.65,'$$n_1=5,n_2=20$$','interpreter','latex','fontsize',18);

text(finv(1-alpha,n1,n2)-1,-0.05,['$$f_{\alpha}(n_1,n_2)=',num2str(finv(0.95,n1,n2)),'$$'],'interpreter',...

   'latex','color','r','fontsize',18);

text(2.43,0.1,'$$\longleftarrow$$','interpreter','latex','fontsize',18,'rotation',45);

text(2.3,0.19,'$$\alpha=0.05$$','interpreter','latex','fontsize',18);

plot(finv(1-alpha,n1,n2),0,'ro','MarkerEdgeColor','r','MarkerFaceColor','r')

xticks([1,2,3,4,5])