matlab练习之程序设计

function y=fun(x)
if x<0&&x~=-3
    y=x.^2+x-6;
elseif x>=0&&x<5&&x~=2&&x~=3
    y=x.^2-5.*x+6;
else
    y=x.^2-x-1;
end
end
----------------------------------
A=[-5 -3 1 2 2.5 3 5];

 for i=1:6
   y(i)=fun(A(i)) ;
end

y

y =

   14.0000   11.0000    2.0000    1.0000   -0.2500    5.0000

function pei =fun(x)
sum=0;
for i=1:x
    sum=sum+1/i^2;
    pei=sqrt(6*sum);
end
pei
end
----------------------------------
fun(10)
ans =

    3.0494

>> fun(100)

ans =
    3.1321
>> fun(10000)
ans =

    3.1415
----------------------------------
方法2
n1=1:100;  
 pai=sqrt(6*sum(1./(n1.*n1)))  
 n2=1:1000;  
 pai=sqrt(6*sum(1./(n2.*n2)))  
 n3=1:10000;  
 pai=sqrt(6*sum(1./(n3.*n3))) 
结果：
n=100 =3.1321
n=1000 =3.1406
n=10000 =3.1415

function pei =fun(a,b)
x(1)=1;
if a<=0||b<=0
    disp(‘error!‘);
end
for i=1:500;
    x(i+1)=a/(x(i)+b);
    if abs(x(i+1)-x(i))<=0.00001
        break;
    end
    
end
x(i)
r1=1/2*(-b+sqrt(b^2+4*a))
r2=1/2*(-b-sqrt(b^2+4*a))
end
--------------------------------------------
 fun(1,1)
ans =
    0.6180
r1 =
    0.6180
r2 =
   -1.6180
>> fun(8,3)
ans =
    1.7016
r1 =
    1.7016
r2 =
   -4.7016
>> fun(10,0.11)
ans =
    3.1078
r1 =
    3.1078
r2 =
   -3.2178