MATLAB编程--基础知识

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：matlab，数据类型（数值，字符串），选择结构，循环接口，函数，字符串函数和矩阵，文件操作

clc

clf

clear

abort

diary filename->diary on->diary off

which filename

editpath

a=[0 1+7]

b=[a(2) 7 a]

定义了数组a=[0 8]和数组b=[8 7 0 8].

d = [1 2]

d(4) = 4

d的值为[1 2 0 4]

first:incr:last

Angles = (.01:.01:1)

Angles = [.01:.01:1]

Angles = .01:.01:1

g = [1:4]‘;

h = [g‘ g‘]

in2 = input(‘enter data:‘,‘s‘) 字符串

c(:,:,1)=[1,2,3;4,5,6];

c(:,:,2)=[1,2,3;4,5,6];

whos c

arr2 = [1 2 3; -2 -3 -4;3 4 5]

子数组arr2(1,:)为[1 2 3]，子数组arr2(:,1:2:3)为第一列，第三列

arr4 = [1 2 3 4;5 6 7 8;9 10 11 12]

arr4(2:end,2:end) 倒过来处理，逆序

str=[‘the value of pi=‘ num2str(pi)];

disp(str);

fprintf(‘The value of pi is %6.2f \n‘,pi)

fprintf 函数只能复数的实部，所以在有复数参加或产生的计算中，可能产生错误的结

果。

save duantest.dat x -ascii

load duantest.dat

.mat

radius = input(‘Enter circle radius:\n‘);

area = pi * radius^2;

str = [‘The area is ‘ num2str(area)]; //类型转换

disp(str);

``在你的MATLAB 代码中，仔细区分数组运算和矩阵运算。数组乘法和矩阵乘法极易混淆。

x=[0 pi/2 3*pi/2 2*pi]

y=sin(x)

x = 0:1:10;

y = x.^2-10*x+15;

plot(x,y);

x=0:1:10;

y=x.^2-10*x+15;

plot(x,y);

title (‘Plot of y=x.^2-10*x+15‘);

xlabel (‘x‘);

ylabel (‘y‘);

grid on;

给图增加标题和坐标轴标签将会用到title, xlabel, ylable 函数。调用每个函数时将会有一

个字符串，这个字符串包含了图象标题和坐标轴标签的信息。用grid 命令可使网格线出现

或消失在图象中，grid on 代表在图象中出现网格线，grid off 代表去除网格线。例如下面的

语句将会产生带有标题，标签和网格线的函数图象

x = 0:pi/100:2*pi;

y1 = sin(2*x);

y2 = 2*cos(2*x);

plot (x,y1,x,y2);

x = 0:1:10;

y = x.^2 -10.*x +15;

plot(x,y,‘r--‘,x,y,‘bo‘);

x=0:pi/100:2*pi;

y1=sin(2*x);

y2=2*cos(2*x);

plot(x,y1,‘k-‘,x,y2,‘b--‘);

title(‘ Plot of f(x)=sin(2x) and its derivative‘);

xlabel(‘x‘);

ylabel(‘y‘);

legend(‘f(x)‘,‘d/dx f(x)‘) %和plot(x,y1,‘k-‘,x,y2,‘b--‘)对应，用于生成图标签

grid on;

%Prompt the user for the input temperature.

temp_f=input(‘Enter the temperature in degrees Fahrenheit:‘);

%Converttokelvins.

temp_k=(5/9)*(temp_f-32)+273.15;

%Writeouttheresult.

fprintf(‘%6.2f degrees Fahrenheit = %6.2f kelvins.\n‘,temp_f,temp_k);

%Set the values of source voltage and internal resistance

volts=120;

rs=50;

%Create an array of load resistances

rl=1:1:100;

%Calculate the current flow for each resistance

amps=volts./(rs+rl);

%Calculate the power supplied to the load

pl=(amps.^2).*rl;

%Plot the power versus load resistance

plot(rl,pl);

title(‘Plot of power versus load resistance‘);

xlabel(‘Load resistance(ohms)‘);

ylabel(‘Power(watts)‘);

grid on;

a = 0;

b = sin(pi);

a == b

ans = 0

if (b^2 - 4*a*c) < 0

disp(‘This equation has two complex roots.‘);

elseif (b^2 - 4*a*c) == 0

disp(‘This equation has two identical real roots.‘);

else

disp(‘This equation has two distinct real roots.‘);

end

%求解二次方程

% Prompt the user for the coefficients of the equation

disp (‘This program solves for the roots of a quadratic ‘);

disp (‘equation of the form A*X^2 + B*X + C = 0.‘);

a = input(‘Enter the coefficient A: ‘);

if a==0

a = input(‘Enter the coefficient A: ‘);

end;

b = input(‘Enter the coefficient B: ‘);

c = input(‘Enter the coefficient C: ‘);

% Calculate discriminant

discriminant = b^2 - 4 * a * c;

% Solve for the roots, depending on the vlaue of the discriminant.

if discriminant > 0 % there are two real roots, so ...

x1 = (-b + sqrt(discriminant)) / (2*a);

x2 = (-b - sqrt(discriminant)) / (2*a);

disp(‘This equation has two real roots:‘);

fprintf(‘x1 = %f\n‘, x1);

fprintf(‘x2 = %f\n‘, x2);

elseif discriminant == 0 % there is one repeated root, so ...

x1 = ( -b ) / (2*a);

disp(‘This equation has two identical real roots:‘);

fprintf(‘x1 = x2 = %f\n‘, x1);

else % there are complex roots, so ...

real_part = (-b) / (2*a);

imag_part = sqrt( abs(discriminant)) / (2*a);

disp(‘This equation has complex roots:‘);

fprintf(‘x1 = %f + i %f \n‘,real_part, imag_part);

fprintf(‘x1 + %f - i %f \n‘, real_part, imag_part);

end

% Prompt the user for the values x and y

x = input(‘Enter the x coefficient: ‘);

y = input(‘Enter the y coefficient: ‘);

% Calculate the function f(x,y) based upon

% the signs of x and y.

if x>=0 & y>=0

fun = x + y;

elseif x>=0 & y<0

fun = x + y^2;

elseif x<0 & y>=0

fun = x^2 + y;

else

fun = x^2 + y^2;

end

% Write the value of the function.

disp([‘The vlaue of the function is ‘ num2str(fun)]);

value = http://www.mamicode.com/input(‘输入一个值：‘);

switch (value)

case {1, 3, 5, 7, 9},

disp(‘The value is odd.‘);

case {2, 4, 6, 8, 10},

disp(‘The value is even.‘);

otherwise,

disp(‘The value is out of range.‘);

end

%将可能出问题的代码放在try中

% Initialize array

a = [ 1 -3 2 5];

try

% Try to display an element

index = input(‘Enter subscript of element to display: ‘);

disp([‘a(‘ int2str(index) ‘) = ‘ num2str(a(index))] );

catch

% If we get here an error occurred

disp( [‘Illegal subscript: ‘ int2str(index)] );

end

意只有带有字符参数的函数才能当作命令。带有数字参数的函数只能被当作函数。这

就是为什么axis 有时当作命令，有时被当作函数。

x = -pi:pi/20:pi;

y1 = sin(x);

y2 = cos(x);

plot(x,y1,‘b-‘);

hold on;

plot(x,y2,‘k--‘);

hold off;

legend (‘sin x‘,‘cos x‘);

%plot(x,y1,‘k-‘,x,y2,‘b--‘);

当hold on 命令执行后，所有的新的图象都会叠

加在原来存在的图象。hold off 命令可恢复默认情况，用新的图象来替代原来的图象。

figure(1);

x = x:0.05:2;%为什么可以X开始，默认为-4

y1 = exp(x);

plot(x,y1);

figure(2);

y2 = exp(-x);

plot(x,y2);

figure(1);

subplot(2,1,1);

x = -pi:pi/20:pi;

y = sin(x);

plot(x,y);

title(‘Subplot 1 title‘);

subplot(2,1,2);

x = -pi:pi/20:pi;

y = cos(x);

plot(x,y);

title(‘Subplot 2 title‘);

x = 0:pi/10:2*pi;

x1 = cos(2*x);

y1 = sin(x);

plot(x1,y1,‘-ro‘,‘LineWidth‘,2.0,‘MarkerSize‘,6,‘MarkerEdgeColor‘,‘b‘,‘MarkerFaceColor‘,‘b‘)

%循环：在循环体中绝不修改循环指数的值。

期望，方差：3，4，5

%first

% Initialize sums.

n = 0; sum_x = 0; sum_x2 = 0;

% Read in first value

x = input(‘Enter first value: ‘);

% While Loop to read input values.

while x >= 0

% Accumulate sums.
n = n + 1;
sum_x = sum_x + x;
sum_x2 = sum_x2 + x^2;
% Read in next value
x = input(‘Enter next value: ‘);

end

% Check to see if we have enough input data.

if n < 2 % Insufficient information

disp(‘At least 2 values must be entered!‘);

else % There is enough information, so

% calculate the mean and standard deviation
x_bar = sum_x / n;
std_dev = sqrt( (n * sum_x2 - sum_x^2) / (n * (n-1)) );
fprintf(‘The mean of this data set is: %f\n‘, x_bar);
fprintf(‘The standard deviation is: %f\n‘, std_dev);
fprintf(‘The number of data points is: %f\n‘, n);

end

%second

% Initialize sums.

sum_x = 0; sum_x2 = 0;

% Get the number of points to input.

n = input(‘Enter number of points: ‘);

% Check to see if we have enough input data.

if n < 2 % Insufficient data

disp (‘At least 2 values must be entered.‘);

else % we will have enough data, so let‘s get it.

% Loop to read input values.
for ii = 1:n
% Read in next value
x = input(‘Enter value: ‘);
% Accumulate sums.
sum_x = sum_x + x;
sum_x2 = sum_x2 + x^2;
end
% Now calculate statistics.
x_bar = sum_x / n;
std_dev = sqrt((n * sum_x2 - sum_x^2) / (n * (n - 1)));
% Tell user.
fprintf(‘The mean of this data set is: %f\n‘, x_bar);
fprintf(‘The standard deviation is: %f\n‘, std_dev);
fprintf(‘The number of data points is: %f\n‘, n);

end

for ii = 1:10

disp([‘test‘ num2str(ii)]);

end

for ii = 1:2:10

disp([‘test‘ num2str(ii)]);

end

for ii = [1 3 5]

disp([‘test‘ num2str(ii)]);

end

for ii = [1 3 5;2 4 6]

jj = ii

end

% Get day, month, and year to convert

disp(‘This program calculates the day of year given the ‘);

disp(‘current date.‘);

month = input(‘Enter current month (1-12):‘);

day = input(‘Enter current day(1-31):‘);

year = input(‘Enter current year(yyyy): ‘);

% Check for leap year, and add extra day if necessary

if mod(year,400) == 0

leap_day = 1; % Years divisible by 400 are leap years

elseif mod(year,100) == 0

leap_day = 0; % Other centuries are not leap years

elseif mod(year,4) == 0

leap_day = 1; % Otherwise every 4th year is a leap year

else

leap_day = 0; % Other years are not leap years

end

% Calculate day of year by adding current day to the

% days in previous months.

day_of_year = day;

for ii = 1:month - 1

% Add days in months from January to last month
switch (ii)
case {1,3,5,7,8,10,12},
  day_of_year = day_of_year + 31;
case {4,6,9,11},
  day_of_year = day_of_year + 30;
case 2,
  day_of_year = day_of_year + 28 + leap_day;

end

% Tell user

fprintf(‘The date %2d/%2d/%4d is day of year %d.\n‘, ...

month, day, year, day_of_year);

%循环

for ii = 1:100

square(ii) = ii ^2;
square_root(ii) = ii ^ (1/2);
cube_root(ii) = ii ^ (1/3);

end

%向量

ii = 1:100;

square = ii .^2;

square_root = ii .^ (1/2);

cube_root(ii) = ii .^ (1/3);

%cube_root = ii .^ (1/3);%结果一样

for 循环算法比向量算法慢15 倍还多

tic; % Start timer

for jj = 1:1000

clear square % Clear output array
ii = 1:10000; % Set up vector
square = ii.^2; % Calculate square

end

average3 = (toc)/1000; % Calculate average time

disp(‘This program performs a leastsquares fit of an ‘);

disp(‘input data set to a straight line.‘);

n_points = input(‘Enter the number of input [x y] points: ‘);

% Read the input data

for ii = 1:n_points

temp = input(‘Enter [x y] pair: ‘);

x(ii) = temp(1);

y(ii) = temp(2);

end

% Accumulate statistics

sum_x = 0;

sum_y = 0;

sum_x2 = 0;

sum_xy = 0;

for ii = 1:n_points

sum_x = sum_x + x(ii);

sum_y = sum_y + y(ii);

sum_x2 = sum_x2 + x(ii)^2;

sum_xy = sum_xy + x(ii) * y(ii);

end

% Now calculate the slope and intercept.

x_bar = sum_x / n_points;

y_bar = sum_y / n_points;

slope = (sum_xy - sum_x * y_bar) / ( sum_x2 - sum_x * x_bar);

y_int = y_bar - slope * x_bar;

% Tell user.

disp(‘Regression coefficients for the leastsquares line:‘);

fprintf(‘ Slope (m) = %8.3f\n‘, slope);

fprintf(‘ Intercept (b) = %8.3f\n‘, y_int);

fprintf(‘ No of points = %8d\n‘, n_points);

% Plot the data points as blue circles with no

% connecting lines.

plot(x,y,‘bo‘);

hold on;

% Create the fitted line

xmin = min(x);

xmax = max(x);

ymin = slope * xmin + y_int;

ymax = slope * xmax + y_int;

% Plot a solid red line with no markers

plot([xmin xmax],[ymin ymax],‘r‘,‘LineWidth‘,2);

hold off;

% Add a title and legend

title (‘\bfLeastSquaresFit‘);

xlabel(‘\bf\itx‘);

ylabel(‘\bf\ity‘);

legend(‘Input data‘,‘Fitted line‘);

grid on

% Constants

conv = pi / 180; % Degreestoradians conversion factor

g = -9.81; % Accel. due to gravity

vo = 20; % Initial velocity

%Create an array to hold ranges

range = zeros(1,91); % Calculate maximum ranges

for ii = 1:91

theta = ii - 1;
vxo = vo * cos(theta*conv);
vyo = vo * sin(theta*conv);
traj_time = -2 * vyo / g;
range(ii) = vxo * traj_time;

end

% Write out table of ranges

fprintf (‘Range versus angle theta:\n‘);

for ii = 1:91

theta = ii - 1;
fprintf(‘ %2d %8.4f\n‘,theta, range(ii));

end

% Calculate the maximum range and angle

[maxrange index] = max(range);

maxangle = index - 1;

fprintf (‘\nMax range is %8.4f at %2d degrees.\n‘,maxrange, maxangle);

% Now plot the trajectories

for ii = 5:10:85

% Get velocities and max time for this angle
theta = ii;
vxo = vo * cos(theta*conv);
vyo = vo * sin(theta*conv);
traj_time = -2 * vyo / g;
% Calculate the (x,y) positions
x = zeros(1,21);
y = zeros(1,21);
for jj = 1:21
time = (jj - 1) * traj_time/20;
x(jj) = vxo * time;
y(jj) = vyo * time + 0.5 * g * time^2;
end
plot(x,y,‘b‘);
if ii == 5
hold on;

end

% Add titles and axis lables

title (‘\bfTrajectory of Ball vs Initial Angle \theta‘);

xlabel (‘\bf\itx \rm\bf(meters)‘);

ylabel (‘\bf\ity \rm\bf(meters)‘);

axis ([0 45 0 25]);

grid on;

% Now plot the max range trajectory

vxo = vo * cos(maxangle*conv);

vyo = vo * sin(maxangle*conv);

traj_time = -2 * vyo / g;

% Calculate the (x,y) positions

x = zeros(1,21);

y = zeros(1,21);

for jj = 1:21

time = (jj - 1) * traj_time/20;
x(jj) = vxo * time;
y(jj) = vyo * time + 0.5 * g * time^2;

end

plot(x,y,‘r‘,‘LineWidth‘,3.0);

hold off

函数：

function out = test1(a, b)

fprintf(‘In Sample: a = %f, b = %f %f\n‘,a,b);

a = b(1) + 2*a;

%b = a .* b;

b=b.*a;

out = a + b(1);

fprintf(‘In Sample: a = %f, b = %f %f \n‘,a,b);

a = 2; b = [6 4];

fprintf(‘Before sample: a = %f, b = %f %f\n‘, a, b);

out = test1(a, b);

fprintf(‘After sample: a = %f, b = %f %f\n‘,a,b);

fprintf(‘After sample: out = %f \n‘, out);

%global

%不能global a = 100;global a; a=100;

%简单随机数发生器的算法。它是利用大数求余的不可预知性

%有问题

function ran = random0(n,m)

global ISEED % Seed for random number generator

% Check for a legal number of input arguments.

ISEED = n;

msg = nargchk(1,2,nargin);

error(msg);

% If the m argument is missing, set it to n.

if nargin < 2

m = n;

end

% Initialize the output array

ran = zeros(n,m);

% Now calculate random values

for ii = 1:n

for jj = 1:m
ISEED = mod(8121*ISEED + 28411, 134456 );
ran(ii,jj) = ISEED / 134456;
end

end

比如在主函数里面，你需要设置data这个变量是一个全局变量，就需要声明一下：
global data;
然后在子函数里面你又用到了data这个全局变量，你需要在子函数里面再次声明：
global data;
这样在子函数中，就可以使用data这个全局变量了

%persistent

%类似于静态变量

function [ave, std] = runstats(x)

% Declare persistent values

persistent n % Number of input values

persistent sum_x % Running sum of values

persistent sum_x2 % Running sum of values squared

% Check for a legal number of input arguments.

msg = nargchk(1,1,nargin);

error(msg);

% If the argument is ‘reset‘, reset the running sums.

if x == ‘reset‘

n = 0;
sum_x = 0;
sum_x2 = 0;

else

n = n + 1;
sum_x = sum_x + x;
sum_x2 = sum_x2 + x^2;

end

% Calculate ave and sd

if n == 0

ave = 0;
std = 0;

elseif n == 1

ave = sum_x;
std = 0;

else

ave = sum_x / n;
std = sqrt((n*sum_x2 - sum_x^2) / (n*(n - 1)));

end

%进行测试

% First reset running sums

[ave std] = runstats(‘reset‘);

% Prompt for the number of values in the data set

nvals = input(‘Enter number of values in data set: ‘);

% Get input values

for ii = 1:nvals

% Prompt for next value
string = [‘Enter value ‘ int2str(ii) ‘: ‘];
x = input(string);
% Get running statistics
[ave std] = runstats(x);
% Display running statistics
fprintf(‘Average = %8.4f; Std dev = %8.4f\n‘,ave, std);

end

%对字符串求值

%eval是解释字符串表达式并求值：eval(‘2^2‘)->4

eval(string)

x = 1;

str = [‘exp(‘ num2str(x) ‘)-1‘];

%str = ‘exp(‘ num2str(x) ‘)-1‘;会进行不同的解析
res = eval(str);

函数feval 对在M 文件进行定义的函数通过其名称进行调用然后求值，要求有指定的输入值。

feval(‘funname‘, value)

%实例

%fun为funname,xlin为x的取值范围[1 4]

function quickplot(fun,xlim)

% Check for a legal number of input arguments.

msg = nargchk(2,2,nargin);

error(msg);

% Check the second argument to see if it has two

% elements. Note that this double test allows the

% argument to be either a row or a column vector.

%size(xlim,1)返回数组的行数，size(xlim,2)返回数组的列数

if ( size(xlim,1) == 1 & size(xlim,2) == 2 ) | ...

( size(xlim,1) == 2 & size(xlim,2) == 1 )
% Ok --continue processing.
n_steps = 100;
step_size = (xlim(2) - xlim(1)) / n_steps;
x = xlim(1):step_size:xlim(2);
y = feval(fun,x);
plot(x,y);
title([‘\bfPlot of function ‘ fun ‘(x)‘]);
xlabel(‘\bfx‘);
ylabel([‘\bf‘ fun ‘(x)‘]);

else

% Else wrong number of elements in xlim.
error(‘Incorrect number of elements in xlim.‘);

end

quickplot(‘sin‘, [-2*pi 2*pi])

常用函数：

nargin 这个函数返回调用这个函数时所需要的实际输入参数的个数

nargout 这个函数返回调用这个函数时所需要的实际输出参数的个数

nargchk 如要一个函数调用被调用时参数过多或过少，那么nargchk 函数将返回一个标

准错误信息

error 显示错误信息，并中止函数以免它产生这个错误。如果参数错误是致命的，这

个函数将会被调用。

warning 显示警告信息并继续执行函数，如果参数错误不是致命的，执行还能继续，则

这个将会被调用。

inputname 这个函数将会返回对于特定参数个数的实际变量名。

rand 产生一个随机数

rand(n) 产生一个n×n 的随机数数组

rand(n,m) 产生一个n×m 的随机数数组

rand 用于产生等可能的随机数

randn 用于产生普通的随机数

a = [‘a‘;‘b‘]

b = char(‘a‘,‘b‘)

函数strcat 水平连接两字符串，忽略所有字符串末端的空格，而字符串的空格保留

result = strcat(‘string 1 ‘,‘String 2‘) ：string 1String 2

result = strvcat(‘Long String 1 ‘,‘String 2‘)

result =

Long String 1

String 2

strcmp 判断两字符串是否等价

strcmpi 忽略大小写判断两字符串是否等价

strncmp 判断两字符串前n 个字符是否等价

strncmpi 忽略大小写判断两字符串前n 个字符是否等价

c = strcmp(‘a’,‘A‘)

c=0

isletter 用来判断一个字符是否为字母

isspace 判断一个字符是否为空白字符（空格，tab，换行符）

a = isletter(‘Room 23a‘ )

a =

1 1 1 1 0 0 0 1

函数findstr 返回短字符串在长字符串中所有的开始位置

position = findstr(‘This is a test!‘ ,‘is‘)

position =

3 6

函数strmatch 看二维数组行开头的字符，并返回那些以指定的字符序列为开头行号

array = strvcat(‘maxarray‘,‘min value‘,‘max value‘);

array = strvcat(‘arraymax‘,‘min value‘,‘max value‘,‘max‘);

result = strmatch(‘max‘,array)

result = upper(‘This is test 1!‘)

result = lower(‘This is test 2!‘)

b = eval(‘3.141592‘)%字符串转换数字

%g:为浮点数

%d:为整数

num2str(1);

int2str(1);

a = [1 2 3; 4 5 6]

b = mat2str(a)

b =

[1 2 3;4 5 6]

单元索引：

a = cell(2, 2)

a{1,1} = [1 3 -7; 2 0 6; 0 5 1];

a{1,2} = ‘This is a text string.‘;

a{2,1} = [3+4*i -5; -10*i 3-4*i];

a{2,2} = [];

a(1,1) ={[1 3 -7; 2 0 6;0 5 1]};

a(1,2) = {‘This is a text string.‘};

a(2,1) = {[3+4*i -5; -10*i 3-4*i]};

a(2,2) = {[]};

b = {[1 2], 17, [2;4]; 3-4*i, ‘Hello‘, eye(3)}

b =

[1x2 double] [ 17] [2x1 double]

[3.0000- 4.0000i] ‘Hello‘ [3x3 double]

celldisk(b)%查看详细信息

b(2,:)=[]%删除第二行

b{1,1}(1,2)%访问单元元素中的元素

结构体：

student.name = ‘a‘;

student.addr1 = ‘b‘;

student.city = ‘c‘;

student.zip = ‘d‘

student为一个数据时：student = student(1)

student(2).name = ‘A‘

student(2)

ans =

name: ‘B‘

addr1: []

city: []

zip: []

stu = rmfield(student, ‘zip‘) %rmfield删除结构体中的域

student(1).name = [1,2,3]

mean(student(1).name)%求平均值

%遍历结构体数组

for ii = 1:length(student)

disp(student(ii).name);

end

f = getfield(array,{array_index},‘field‘,{field_index})

zip = getfield(student,{2})

zip =

name: ‘B‘

addr1: []

city: []

zip: []

zip = getfield(student,{2},‘name‘)

zip =

f = setfield(array,{array_index},‘field‘,{field_index},value) %？？？？？

结构体嵌套：

student(1).class(1).name = ‘COSC 2021‘;

student(1).class(2).name = ‘PHYS 1001‘;

student(1).class(1).instructor = ‘Mr. Jones‘;

student(1).class(2).instructor = ‘Mrs. Smith‘;

matlab文件操作

fid = fopen(filename, permission)

[fid, message] = fopen(filename, permission)

[fid, message] = fopen(filename,permission, format)

如果文件被成功打开，在这个语句执行之后，fid 将为一个正整数，message 将为一个空字符。如果文件打开失败，在这个语句执行

之后，fid 将为-1，message 将为解释错误出现的字符串

fid = fopen(‘example.dat‘,‘r‘)

status = fclose(example.dat) %成功为0，失败为-1

%实例对文件进行读写

filename = input(‘Enter file name: ‘,‘s‘);

% Generate the data array

out_array = randn(1,10000);

% Open the output file for writing.

[fid,msg] = fopen(filename,‘w‘);

% Was the open successful?

if fid > 0

% Write the output data.
count = fwrite(fid,out_array,‘float64‘);
% Tell user
disp([int2str(count) ‘ values written...‘]);
% Close the file
status = fclose(fid);

else

% Output file open failed. Display message.
disp(msg);

end

% Now try to recover the data. Open the

% file for reading.

[fid,msg] = fopen(filename,‘r‘);

% Was the open successful?

if fid > 0

% Read the input data.
[in_array, count] = fread(fid,[100 100],‘float64‘);
% Tell user
disp([int2str(count) ‘ values read...‘]);
% Close the file
status = fclose(fid);

else

% Input file open failed. Display message.
disp(msg);

end

fprintf(‘ Table of Square Roots, Squares, and Cubes\n\n‘);

% Print column headings

fprintf(‘ Number Square Root Square Cube\n‘);

fprintf(‘ ====== =========== ====== ====\n‘);

% Generate the required data

ii = 1:10;

square_root = sqrt(ii);

square = ii.^2;

cube = ii.^3;

% Create the output array

out = [ii‘ square_root‘ square‘ cube‘];%将行转换成列

% Print the data

for ii = 1:10

fprintf (‘ %2d %11.4f %6d %8d\n‘,out(ii,:));

end

ident = exist(‘item‘); %ident的取值含义

out_filename = input(‘Enter output filename: ‘,‘s‘);

% Check to see if the file exists.

if exist(out_filename,‘file‘)

% The file exists
disp(‘Output file already exists.‘);
yn = input(‘Keep existing file? (y/n) ‘,‘s‘);
if yn == ‘n‘
fid = fopen(out_filename,‘wt‘);

else

fid = fopen(out_filename,‘at‘);

end

else

% File doesn‘t exist
fid = fopen(out_filename,‘wt‘);

end

% Output data

fprintf(fid,‘%s\n‘,date);

% Close file

fclose(fid);

fid=fopen(‘fgetl.m‘);

while 1

tline = fgetl(fid);

if ~ischar(tline), break, end

disp(tline)

end

fclose(fid);

fid = fopen(‘exp.txt‘,‘w‘);

fprintf(fid,‘%6.2f %12.8f\n‘,y);

fclose(fid);

%执行fclose后内容才会写到文件中去

MATLAB编程--基础知识

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