1

lab4/exercise4_1.m

@@ -0,0 +1,10 @@
+c = input('请输入一个字符：', 's');
+if c >= 'A' && c <= 'Z'
+    disp(char(abs(c) + abs('a') - abs('A')));
+elseif c >= 'a' && c <= 'z'
+    disp(char(abs(c) - abs('a') + abs('A')));
+elseif c >= '0' && c <= '9'
+    disp(abs(c) - abs('0'));
+else
+    disp(c);
+end

lab4/exercise4_10.m

@@ -0,0 +1,6 @@
+mysum=0,i=1;
+while(i<=100)
+    mysum=mysum+i
+    i=i+1 ;
+end
+mysum

lab4/exercise4_11.m

@@ -0,0 +1,13 @@
+A=[1 2 3;4 5 6;7 8 9];
+[r,c]=size(A);
+% 判断并把A中大于8和小于2的元素全部调整为0
+for i=1:1:r
+    for j=1:1:c
+        if (A(i,j)>8 || A(i,j)<2)
+            A(i,j)=0;
+        end
+    end
+end
+% 改写
+b=(A <= 8 & A >= 2); % 判断A中小于等于8和大于等于2的元素，结果是逻辑值0/1
+A=A.*b %实现A中大于8和小于2的元素全部调整为0，基于矩阵的点乘

lab4/exercise4_12.m

@@ -0,0 +1,5 @@
+x = 0:0.05:2;
+y = diag(f(x).*f(x+2));
+plot(x,y);
+xlabel('\bfx');
+ylabel('\bfy');

lab4/exercise4_13.m

@@ -0,0 +1,8 @@
+subplot(2,2,2);
+x=linspace(-pi/2,pi/2,100);
+y=sqrt(cos(x));
+plot(x,y);
+subplot(2,2,3);
+x=linspace(-2,2);
+y=linspace(-4,4);
+ezsurfc('x.^2/4+y.^2/16')

lab4/exercise4_14.m

@@ -0,0 +1,9 @@
+A=input('请输入一个向量');
+[m,n]=size(A);
+min=A(1,n);
+for i=1:n
+    if min>A(1,i)
+        min=A(1,i);
+    end
+end
+disp(min)

lab4/exercise4_15.m

@@ -0,0 +1,6 @@
+a=[2,3,1,2;1,3,0,1;1,-1,1,8;7,1,-2,2];
+b=[8,6,1,5]';
+ra=rank(a);
+rb=rank([a,b]);
+det(a);
+xx=a\b

lab4/exercise4_16.m

@@ -0,0 +1,9 @@
+t=linspace(0,4*pi,20);
+y1=sin(t);
+y2=2*cos(2*t);
+plot(t,y1,'k-');
+text(1.2,sin(1.2),'y1 \leftarrow','FontSize',12)
+hold on;
+plot(t,y2,'r--o');
+text(6,1.5,'y2 \leftarrow','FontSize',12);
+title('y1 and y2');

lab4/exercise4_2.m

@@ -0,0 +1,6 @@
+a=input('a=?');
+b=input('b=?');
+c=input('c=?');
+d=b*b-4*a*c;
+x=[(-b+sqrt(d))/(2*a),(-b-sqrt(d))/(2*a)]; 
+disp(['x1 =',num2str(x(1)),' ,x2=',num2str(x(2))]);

lab4/exercise4_3.m

@@ -0,0 +1,7 @@
+x=input('请输入x的值:');
+if x==10
+    y=cos(x+1)+sqrt(x*x+1);
+else
+    y=(3^(1/2))*sqrt(x+sqrt(x));
+end
+y

lab4/exercise4_4.m

@@ -0,0 +1,6 @@
+s=0;
+a=[12,13,14;15,16,17;18,19,20];
+for k=a
+    s=s+k;
+end
+disp(s');

lab4/exercise4_5.m

@@ -0,0 +1,9 @@
+k=0;
+for n=100:200
+    if rem(n,21)~=0
+        k=k+1;
+    continue
+    end
+break;
+end
+k

lab4/exercise4_7.m

@@ -0,0 +1,9 @@
+x=-2:0.2:2;
+y=x.^2;
+plot(x,y)
+str1 = num2str(min(x));
+%数字转化为字符串
+str2 = num2str(max(x)); 
+%数字转化为字符串
+out = ['Value of f from ''str1'' to ''str2'' '];
+xlabel(out);

lab4/exercise4_8.m

@@ -0,0 +1,13 @@
+s1=0;s2=0;n1 =0;n2=0 ;
+x=[1,-4,-8,3,10,-9,7,-3,10, 8,-5,-2,2,0];
+m=length(x);
+for i=1:m
+    if x(i)<0
+        s1=s1+x(i);
+        n1=n1+1;
+    else
+        s2=s2+x(i);
+        n2=n2+1;
+    end
+end
+s1,n1 ,s2,n2,m

lab4/exercise4_9.m

@@ -0,0 +1,4 @@
+A=[1,2;3,4];B=[1,2;1,4];
+C= A*B
+D= A+B
+E= A.*B

lab4/f.m

@@ -0,0 +1,8 @@
+function y=f(x)
+if x<=2
+    y=0.5*x;
+elseif x>6
+    y=0.5;
+else
+    y =1.5-0.25*x;
+end

lab4/factor.m

@@ -0,0 +1,6 @@
+function f=factor(n)
+if n<=1
+    f=1;
+else
+    f=factor(n-1)*n;
+end