MATLAB练习例子十一(M文件编辑)
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<![CDATA[
Logical Expressions Using the find Function
》 A = magic(4)
A =
16 2 3 13
5 11 10 8
9 7 6 12
4 14 15 1
》 i = find(A>8);
》 A(i) = 100
A =
100 2 3 100
5 100 100 8
100 7 6 100
4 100 100 1
logical operators
》 u = [1 0 2 3 0 5];
》 v = [5 6 1 0 0 7];
》 u & v
ans =
1 0 1 0 0 1
》 u | v
ans =
1 1 1 1 0 1
》 ~u
ans =
0 1 0 0 1 0
》 a = 1;
》 b = 1;
》 xor(a,b)
ans =
0
》 A = [0 1 2;3 5 0]
A =
0 1 2
3 5 0
》 all(A)
ans =
0 1 0
》 v = [5 0 8];
》 any(v)
ans =
1
》
》 A = magic(3)
A =
8 1 6
3 5 7
4 9 2
》 3 * A
ans =
24 3 18
9 15 21
12 27 6
Relational operators
》 A = [2 7 6; 9 0 5; 3 0.5 6];
》 B = [8 7 0; 3 2 5; 4 -1 7];
》 A == B
ans =
0 1 0
0 0 1
0 0 0
》 A == []
Warning: X == [] is technically incorrect. Use isempty(X) instead.
ans =
0
》 isempty(A)
ans =
0
》
一些常用变量
》 eps
ans =
2.2204e-016
》 realmax
ans =
1.7977e+308
》 realmin
ans =
2.2251e-308
》 pi
ans =
3.1416
》 computer
ans =
PCWIN
》 version
》 x = 2*pi;
》 x
x =
6.2832
》 A = [3+2i 7-8i]
A =
3.0000 + 2.0000i 7.0000 - 8.0000i
》 tol = 3*eps
tol =
6.6613e-016
》
function yp = lotka(t,y)
%LOTKA Lotka-Volterra predator-prey model.
global ALPHA BETA
yp = [y(1) - ALPHA*y(1)*y(2); -y(2) + BETA*y(1)*y(2)];
》 global ALPHA BETA
》 ALPHA = 0.01
ALPHA =
0.0100
》 BETA = 0.02
BETA =
0.0200
》 [t,y] = ode23('m0_lotka',0,10,[1;1]);
Warning: Obsolete syntax. ode23("m0_lotka",tspan,y0,...)を代わりに使ってください
> In C:\MATLAB\toolbox\matlab\funfun\ode23.m at line 100
》 plot(t,y)
function m005(varargin)
for i = 1:length(varargin)
x(i) = varargin{i}(1); % Cell array indexing
y(i) = varargin{i}(2);
end
xmin = min(0,min(x));
ymin = min(0,min(y));
axis([xmin fix(max(x))+3 ymin fix(max(y))+3])
plot(x,y)
》 m005([2 3],[1 5],[4 8],[6,5],[2,4])
function c = m004(a,b)
% m004.m
if (nargin == 1)
c = a.^2;
elseif (nargin == 2)
c = a + b;
end
》 m004 2
ans =
2500
》 m004 1
ans =
2401
》 m004 2 2
ans =
100
function y = average(x)
% AVERAGE Mean of vector elements. m003.m
% AVERAGE(X), where X is a vector, is the mean of vector elements.
% Non-vector input results in an error.
[m,n] = size(x);
if (~((m == 1 ) | (n == 1)) | (m == 1 & n == 1))
error('Input must be a vector')
end
y = sum(x)/length(x);
》 z = 1:99;
》 m003(z)
ans =
50
function c = m001(a,b)
c = sqrt((a.^2)+(b.^2))
》 a = 7.5
a =
7.5000
》 b = 3.342
b =
3.3420
》 c = m001(a,b)
c =
8.2109
c =
8.2109
》
列出文件名
what/dir
显示M文件的内容(设存在file.m)
type file
% An M-file script to produce, m002.m
% "flow petal" plots
theta = -pi:0.01:pi;
rho(1,:) = 2*sin(5*theta).^2;
rho(2,:) = cos(10*theta).^3;
rho(3,:) = sin(theta).^2;
rho(4,:) = 5*sin(3.5*theta).^3;
for i = 1:4
polar(theta,rho(i,:))
pause
end
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求[0,1]范围的n个随机数
n = input('Enter n ');
x = rand(1,n)
xmax = max(x)
xmin = min(x)
y = sort(x)
运行结果
Enter n 5
x =
0.6154 0.7919 0.9218 0.7382 0.1763
xmax =
0.9218
xmin =
0.1763
y =
0.1763 0.6154 0.7382 0.7919 0.9218
x = input('Enter x ');
tf = input('Enter tf ');
A = [0.8 1; 0 0.8]
y = [];
for i = 1:tf+1
y(:,i) = x;
x = A*x;
end
y
》 test18
Enter x [1 1]
Enter tf 2
A =
0.8000 1.0000
0 0.8000
??? 割り当て A(:,matrix) = B では、A のサブスクリプトの要素数と B の列数が同じである必要があります
エラー: ==> C:\test\test18.m
行番号: 7 ==> y(:,i) = x;
-------------------------------------------------
计算阶乘
n = input('Enter n ');
y = 1;
for i = 1:n
y = y*i;
end
y
n = input('Enter n ');
x = 1:n
y = prod(x)
进行累加的程序
n = input('Enter name ');
s = 0;
for i = 1:n
s = s + i;
end
s
计算y=1+x+x2+...+xn
x = input('Enter x ');
n = input('Enter n ');
a = 1;
y = 1;
for i = 1:n
a = a*x;
y = y + a;
end
y
Enter x 1.01
Enter n 100
y =
173.1862
user_entry = input('prompt', 's') returns the entered string as a text variable rather than as a variable name or numerical value.
name1 = input('Enter name ','s');
画面输出到文件中去
diary(outputf)
--------------------------------------------
name1 = input('Enter name ','s');
output1 = '_out.txt';
outputf = strcat(name1,output1)
diary(outputf)
x11 = '_x11.txt';
fx11 = strcat(name1,x11);
X11 = dlmread(fx11,';')
x12 = '_x12.txt';
fx12 = strcat(name1,x12);
X12 = dlmread(fx12,';')
x21 = '_x21.txt';
fx21 = strcat(name1,x21);
X21 = dlmread(fx21,';')
x22 = '_x22.txt';
fx22 = strcat(name1,x22);
X22 = dlmread(fx22,';')
#计算逆矩阵
X22inv = inv(X22);
X = X11 - X12 * X22inv * X21
diary off
-------------------------------------
n = input('Enter n ');
switch n
case -1
disp('minus one');
case 0
disp('zero');
case 1
disp('one');
otherwise
disp('other value');
end
》 test8
Enter n 1
one
》 test8
Enter n 0
zero
》 test8
Enter n -1
minus one
》 test8
Enter n 99
other value
n = input('Enter n ');
switch n
case 1
disp('1');
case {2,3,4}
disp('2 or 3 or 4');
case 5
disp('5');
otherwise
disp('other value');
end
》 test9
Enter n 3
2 or 3 or 4
》 test9
Enter n 1
1
》 test9
Enter n 5
5
》 test9
Enter n 88
other value
》
eps = 0.001;
a = input('Enter a ');
while a >= eps
a = a*0.5
end
》 test10
Enter a 2
a =
1
a =
0.5000
a =
0.2500
a =
0.1250
a =
0.0625
a =
0.0313
a =
0.0156
a =
0.0078
a =
0.0039
a =
0.0020
a =
9.7656e-004
》
test1.m
A = input('Enter matrix A ')
》 test1
Enter matrix A [1 2 3; 4 5 6; 7 8 9]
A =
1 2 3
4 5 6
7 8 9
》
test2.m
A = input('Enter matrix A ')
B = input('Enter matrix B ')
X = A + B
Y = A - B
》 test2
Enter matrix A [1 2 3; 4 5 6; 7 8 9]
A =
1 2 3
4 5 6
7 8 9
Enter matrix B [1 -1 1; 2 2 -1; -1 2 1]
B =
1 -1 1
2 2 -1
-1 2 1
X =
2 1 4
6 7 5
6 10 10
Y =
0 3 2
2 3 7
8 6 8
function sequence = collatz(n)
sequence = n;
next_value = n;
while next_value > 1
if rem(next_value,2) == 0;
next_value = next_value / 2;
else
next_value = 3*next_value + 1;
end
sequence = [sequence, next_value];
end
function collatzplot(n)
clf
set(gcf,'DoubleBuffer','On')
set(gca,'XScale','linear')
for m = 1:n
plot_seq = collatz(m);
seq_length(m) = length(plot_seq);
line(m,plot_seq,'Marker','.','MarkerSize',9,'Color','blue')
drawnow
end
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collatzplot(500)
<![CDATA[
描画sin曲线
t = 0:0.01:10;
y = sin(t);
plot(t,y)
grid on
描画cos曲线
t = 0:0.01:10;
y = cos(t);
plot(t,y)
grid on
描画tan曲线
t = 0:0.01:10;
y = tan(t);
plot(t,y)
grid on
描画一个sin曲线
t = 0:5:300;
y = 0.5*sin(t*pi/300);
plot(t,y)
grid on
描画一个cosech曲线
t = 5:5:295;
y = 0.5*csch(t*pi/300);
plot(t,y)
grid on
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<![CDATA[
x = input('Enter x ');
if x > 0
y = 1;
elseif x<0
y = -1;
else
y = 0;
end
y
》 test7
Enter x 0
y =
0
》 test7
Enter x 3
y =
1
》 test7
Enter x -2
y =
-1
》
-------------------------------------------
x = input('Enter x ');
if x >= 0
y = 1;
else
y = -1;
end
y
》 test6
Enter x 8
y =
1
》 test6
Enter x -9
y =
-1
》
-------------------------------------------
a = input('Enter a ');
b = input('Enter b ');
if b ~= 0
y = a/b
end
》 test5
Enter a 10
Enter b -5
y =
-2
》 test
??? 'test' は未定義の関数、または変数です.
》 test5
Enter a 100
Enter b 0
》 test5
Enter a 222
Enter b 11
y =
20.1818
》
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