20150319_Pra

1.to create a serial number doesn't repeat
N = fix(91*rand(1,10))+9

2.to empty a row or col
X=magic(4)
X(3,:)=[]

3.draw a tangent function
t=-1.5:0.01:1.5
y=tan(t);
plot(t,y)

4.
t = 0:pi/10:2*pi;
plot(exp(i*t),'-o') % -o : plot circle ; -s : plot square
axis equal
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t = 0:pi/10:2*pi;
x=3*cos(t);
y=3*sin(t);
plot(x,y)

5.
save TD -ascii

6.load image and flip it
 load durer
 X=(X/5);
 image(X)
 Y=fliplr(X);
 image(Y)

7.root for polynomial x^3 + x + 1 = 0
p=[1,0,1,1];
x=roots(p)

8.find the numbers less than 0
X=randn(4)
size(X(find(X<0)),1)
%k=find(X<0)
%length(k)

9.find eigenvalue and eigenvector for a matrix
x=magic(3)
y=eig(x)
det(x)
v = ones(3,1)
x*v


10.
for i =1:sqrt(int_v)
        if 2^i >int_v
            break
        end
    end
i
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n=1;
p=2^n;
while (x>p)
    p=p*2;
    n=n+1;
end
n