chap01MATLAB基本使用方法.ppt

1 MATLAB基本使用方法 hjT 西安电子科技大学理学院 2 主要内容 n简单的数学运算 n标点符号的使用 n常量与变量 n常用数学函数 n浮点数与复数 n逻辑运算 n向量 3 简单的数学运算 n直接输入 n存储变量 n抑制输出 n注释 format compact 4*30 + 3*35 ans = 225 grade1 = 4*30 grade1 = 120 grade2 = 3*35 grade2 = 105 total = grade1 + grade2 total = 225 grade1 = 4*30; % 一班的人数 grade2 = 3*35; % 二班的人数 total = grade1 + grade2 % 总人数 total = 225 4*30 + 3*35 ans = 225 ans * 2 ans = 450 ans * 2 % 再来 ans = 900 4 指令中的标点 n逗号 x = sin(1), y = cos(1), z = tan(1), w = atan(1) x = 0.8415 y = 0.5403 z = 1.5574 w = 0.7854 5 指令中的标点 n续行号 grade1 = 4 * . 30 grade1 = 120 grade2 = 3 * . 35 35 grade2 = 105 total = grade1 + gra. de2 ? de2 | Error: Unexpected MATLAB expression. 6 指令中的标点符号 n空格 分隔符：机器辨认；数组元素分隔 n逗号, 分隔（同空格）；显示计算结果指令间的分割 n黑点. 3.14159；数组运算符(.*, ./, .等) n分号; 屏蔽输出；A=1 2; 3 4; B=5, 6; 7, 8; C=A+B n冒号: 1:10, 10:-1:1；单下标引用(A(:)、多下标引用(A(:, 1), A(2, :) 7 指令中的标点符号 n% 注释号 n 字符串 n() 改变运算次序；数组引用A(1, 2), 输入参 数列表 n 数组输入时构成矩阵；函数输出列表 n 胞元数组；图形中被控制的特殊字符括号 8 指令中的标点符号 n_ 下连符 作为变量、函数名字中的字符 图形中被控下标前导符 n 续行符 n 放在函数名前，形成函数句柄； 匿名函数前导符 放在目录名前，形成“用户对象”类目录 9 常量 nInf | inf nNaN | nan ni, j 1/0 Warning: Divide by zero. ans = Inf 0/0 Warning: Divide by zero. ans = NaN 1/inf ans = 0 0*inf ans = NaN sqrt(-1) ans = 0 + 1.0000i i-j ans = 0 10 常量 npi format long pi ans = 3.141592653589793 sin(3.141592653589793) ans = 1.224646799147353e-016 sin(pi) ans = 1.224646799147353e-016 sin(pi*1e10) ans = -2.239362761955923e-006 clear cos(pi) ans = -1 pi = 10 pi = 10 cos(pi) ans = -0.839071529076452 clear cos(pi) ans = -1 11 变量的命名规则 n变量名大小写敏感 Var, var, vAr, vaR, vAR, VAr, VaR, VAR 各不相同 n第一个必须是英文字母，最多63个字符(英 文、数字和下划线) A101_35, room101_24_up 12 常用数学函数 nsin, cos, tan, cot, csc, sec; nasin, acos, atan, acot, acsc, asec nsinh, cosh, tanh, coth csch, sech nasinh, acosh, atanh, acoth, acsch, asech nexp, log, log2, log10, pow2, , sqrt nreal, imag, abs, angle, conj, isreal nfix, floor, ceil, round % 0, -inf, +inf nmod, rem % fix, floor nsign, beta, gamma, erf, cross nmax, min, sum, mean, std n 13 浮点数 n双精度表示误差 format long a = 0.33 + 0.17 - 0.5 a = 0 b = 0.33 - 0.5 + 0.17 b = 2.775557561562891e-017 c = 0.17 - 0.5 + 0.33 c = 5.551115123125783e-017 eps ans = 2.220446049250313e-016 realmax, realmin, . 1/realmax, 1/realmin ans = 1.797693134862316e+308 ans = 2.225073858507201e-308 ans = 5.562684646268004e-309 ans = 4.494232837155790e+307 pow2(1023), pow2(1024), . pow2(-1074), pow2(-1075) ans = 8.988465674311580e+307 ans = Inf ans = 4.940656458412465e-324 ans = 0 14 复数 n进行复数处 理时，不需 要进行任何 其他附件操 作 n只有常数才 能与i/j直接相 连 a1 = pi + 3.14i a1 = 3.1416 + 3.1400i a2 = pi + 3.14j a2 = 3.1416 + 3.1400i b = 4*(1 + 3/sqrt(-1) b = 4.0000 -12.0000i c = sqrt(-1) c = 0 + 1.0000i d = sin(pi)i ? d = sin(pi)i | Error: Unexpected MATLAB expression. d = sin(pi)*i d = 0 +1.2246e-016i 15 复数的数学运算举例 a = 1 + 2*i a = 1.0000 + 2.0000i b = 3 - 4*i; c = pi + sin(pi/2)*i c = 3.1416 + 1.0000i d = a + b d = 4.0000 - 2.0000i e = a*d e = 8.0000 + 6.0000i f = a/e f = 0.2000 + 0.1000i g = af g = 1.0040 + 0.3127i 16 关系与逻辑运算 n关系操作符 , =, a = 2; b = 3; a b | b a ans = 1 a b 10; 11; 12 a3 = 9 10 11 12 a3 ans = 9 10 11 12 19 等差元素向量的输入 v1 = 1:9 v1 = 1 2 3 4 5 6 7 8 9 v2 = 10:5:50 v2 = 10 15 20 25 30 35 40 45 50 v3 = 50:-5:9 v3 = 50 45 40 35 30 25 20 15 10 v4 = linspace(10, 50, 6) v4 = 10 18 26 34 42 50 v4 = linspace(10, 50, 7) v4 = 10.0000 16.6667 23.3333 30.0000 36.6667 43.3333 50.0000 20 等比元素向量的输入 v6 = logspace(0, 3, 4) v6 = 1 10 100 1000 a = 1; b = 100; n = 10; v = logspace(log10(a), log10(b), n) v = Columns 1 through 5 1.0000 1.6681 2.7826 4.6416 7.7426 Columns 6 through 10 12.9155 21.5443 35.9381 59.9484 100.0000 plot(v, v*0, +-); 21 向量的基本运算 n向量与数的四则运算 n向量与向量之间的加减运算 n点积、叉积、混合积 n向量的比较、查找 22 向量与数的四则运算 v1 = 1:5 v1 = 1 2 3 4 5 v1 + 100 ans = 101 102 103 104 105 v1 * 100 ans = 100 200 300 400 500 v1 / 5 ans = 0.2000 0.4000 0.6000 0.8000 1.0000 5v1 ans = 0.2000 0.4000 0.6000 0.8000 1.0000 23 向量与向量之间的加减运算 v1 = linspace(10, 50, 6) v1 = 10 18 26 34 42 50 v2 = logspace(0, 2, 6) v2 = 1.0000 2.5119 6.3096 15.8489 39.8107 100.0000 v3 = v1 + v2 v3 = 11.0000 20.5119 32.3096 49.8489 81.8107 150.0000 v4 = v3 - v2 v4 = 10.0000 18.0000 26.0000 34.0000 42.0000 50.0000 v5 = v4 - v1 v5 = 1.0e-014 * 0 0 0 0 -0.7105 0 24 点积、叉积、混合积 n数组操作 .+, .-, .*, ./, . v1 = 1:5 v1 = 1 2 3 4 5 v2 = 6:10 v2 = 6 7 8 9 10 v3 = v1.*v2 v3 = 6 14 24 36 50 v4 = v3./v2 v4 = 1 2 3 4 5 v6 = v1.2 v6 = 1 4 9 16 25 v7 = 2.v1 v7 = 2 4 8 16 32 v8 = v1.(5-v1) v8 = 1 8 9 4 1 v9 = v1.(6-v1) v9 = 1 16 27 16 5 v10 = v1.(6.-v1) v10 = 1 16 27 16 5 25 点积、叉积、混合积 n点积 dot(a, b) n叉积 cross(a, b) n混合积 dot(a, cross(b, c) 顺序不能颠倒！ a = 1:3; b = 4:6; c = dot(a, b) c = 32 sum(a.*b) ans = 32 d = cross(a, b) d = -3 6 -3 dot(a, d), dot(b, d) ans = 0 ans = 0 26 向量的下标操作 a = 100 + (1:10) a = 101 102 103 104 105 106 107 108 109 110 a(4) ans= 104 b = a(2:5) b = 102 103 104 105 d = a(5:-1:2) d = 105 104 103 102 c = 7:10 c = 7 8 9 10 f = a(c) f = 107 108 109 110 27 向量的下标操作 a a = 101 102 103 104 105 106 107 108 109 110 size(a) ans = 1 10 length(a) ans = 10 a(5:end) ans = 105 106 107 108 109 110 a(end:-1:5) ans = 110 109 108 107 106 105 A = ; size(A) ans = 0 0 length(A) ans = 0 A = 1:10; A(1:end) = ; size(A) ans = 1 0 length(A) ans = 0 28 向量的统计操作 disp(a) 101 102 103 104 105 106 107 108 109 110 sum(a) ans = 1055 max(a) ans = 110 min(a) ans = 101 mean(a) ans = 105.5000 std(a) ans = 3.0277 29 向量的比较 a a 108 ans = 0 0 0 0 0 0 0 0 1 1 a(a a(a 108) ans = 109 110 30 向量的比较 disp(a); disp(b); 101 102 103 104 105 106 107 108 109 110 110 109 108 107 106 105 104 103 102 101 a b ans = 0 0 0 0 0 1 1 1 1 1 a c = fliplr(a) c = 110 109 108 107 106 105 104 103 102 101 c = b ans = 1 1 1 1 1 1 1 1 1 1 a = b ans = 0 0