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//%以定义average函数举例
%1
function y= average(x);//x must be a vector
y=sum(x)/length(x);
>>z=1:99
average(z)
>>ans=50
//2 定义可以output mean and standard deviation的函数
function [m,s]=fun_name(x)
n=length(x);
m=sum(x)/n;
s=sqrt(sum((x-m).^2/n);
//call the function from the command line
>>values=[somenumbers...];
[m,s]=fun_name(values)
//define 2 functions in 1 file(and the file name is fun1.m)
function [m,s]=fun_name(x)
n=length(x);
m=average(x)/n;
s=sqrt(sum((x-m).^2/n));//just use "func. average" in fun. two
end
function y= average(x)
y=sum(x)/length(x);
end
//ATTN average is a local function, only available to other functionswithin the same file

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function [xbar,s]=ex2_1(x)
n=length(x);
xbar=sum(x)/n;
s=sqrt((sum(x.^2)-n*xbar^2)/(n-1));

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clear;
F(1)=1;F(2)=1;k=2;x=0; %这里取x=0的目的是保证后面abs(x-a)>e成立
e=1e-8; a=(1+sqrt(5))/2;
while abs(x-a)>e
k=k+1;F(k)=F(k-1)+F(k-2); x=F(k)/F(k-1);
end
a,x,k 

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clc;clear;
tic;
s=0;
for i=1:10^6
s=s+(3^(1/2))/2^i;
end
s
toc

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tic;
s=0;i=1;
while i<=1000000
s=s+sqrt(3)/2^i;i=i+1;
end
s,
toc

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tic;
s=0;
i=1:1000000;
s=sqrt(3)*sum(1./2.^i);
s
toc

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clear
time=0:1:24;
tem=[15,14,14,14,14,15,16,18,20,22,23,25,28,31,32,31,29,27,25,24,22,20,18,17,16];
plot(time,tem)

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%(1)
x=-2:0.1:2;
y=x.^2.*sin(x.^2-x-2);
plot(x,y)
y=inline('x^2*sin(x^2-x-2)');
% or y=(x.^2).*sin(x.^2-x-2);
fplot(y,[-2 2])

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%2
t=linspace(0,2*pi,100); %注意步长取法，不要简单用t=0:0.1:2*pi，否则造成椭圆缺口
x=2*cos(t);y=3*sin(t); plot(x,y)
%2
ezplot('(x.^2)./4+(y.^2)./9 = 1')