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1、第二章数值数组及其运算2.1引导【例2.1-1】绘制函数在时的曲线（见图2.1-1）。x=0:0.1:1y=x.*exp(-x)plot(x,y),xlabel('x'),ylabel('y'),title('y=x*exp(-x)')x=Columns1through700.10000.20000.30000.40000.50000.6000Columns8through110.70000.80000.90001.0000y=Columns1through700.09050.16370.22220.26810.30330.3
2、293Columns8through110.34760.35950.36590.3679图2.1-12.2一维数组的创建和寻访2.2.1一维数组的创建（1）逐个元素输入法x=[2pi/2sqrt(3)3+5i]x=2.00001.57081.73213.0000+5.0000i（2）冒号生成法（3）定数线性采样法2.2.2一维数组的子数组寻访和赋值【例2.2-1】子数组的寻访（Address）。rand('state',0)x=rand(1,5)x=0.95010.23110.60680.48600.8913x(3)ans=1
3、40.6068x([125])ans=0.95010.23110.8913x(1:3)ans=0.95010.23110.6068x(3:end)ans=0.60680.48600.8913x(3:-1:1)ans=0.60680.23110.9501x(find(x>0.5))ans=0.95010.60680.8913x([12344321])ans=Columns1through70.95010.23110.60680.48600.48600.60680.2311Column80.9501【例2.2-2】子数组的赋值（A
4、ssign）。x(3)=0x=0.95010.231100.48600.8913x([14])=[11]x=1.00000.231101.00000.89132.1二维数组的创建2.1.1直接输入法【例2.3-1】在MATLAB环境下，用下面三条指令创建二维数组C。a=2.7358;b=33/79;C=[1,2*a+i*b,b*sqrt(a);sin(pi/4),a+5*b,3.5+i]C=1.00005.4716+0.4177i0.69090.70714.82443.5000+1.0000i【例2.3-2】复数数组的另一种输
5、入方式。M_r=[1,2,3;4,5,6],M_i=[11,12,13;14,15,16]CN=M_r+i*M_iM_r=123456M_i=11121314151614CN=1.0000+11.0000i2.0000+12.0000i3.0000+13.0000i4.0000+14.0000i5.0000+15.0000i6.0000+16.0000i2.1.1利用M文件创建和保存数组【例2.3-3】创建和保存数组AM的MyMatrix.m文件。%MyMatrix.mCreationandpreservationofmatr
6、ixAMAM=[101,102,103,104,105,106,107,108,109;...201,202,203,204,205,206,207,208,209;...301,302,303,304,305,306,307,308,309];2.2二维数组元素的标识2.2.1“全下标”标识2.2.2“单下标”标识2.2.3“逻辑1”标识【例2.4-1】找出数组中所有绝对值大于3的元素。A=zeros(2,5);A(:)=-4:5L=abs(A)>3islogical(L)X=A(L)A=-4-2024-3-1135L=10
7、00100001ans=1X=-4452.3二维数组的子数组寻访和赋值【例2.5-1】不同赋值方式示例。A=zeros(2,4)A=00000000A(:)=1:8A=13572468s=[235];14A(s)Sa=[102030]'A(s)=Saans=235Sa=102030A=12030710468A(:,[23])=ones(2)A=1117101182.1执行数组运算的常用函数2.1.1函数数组运算规则的定义：2.1.2执行数组运算的常用函数2.2数组运算和矩阵运算2.2.1数组运算和矩阵运算指令对照汇总【例2.7
8、-1】两种不同转置的比较clear;A=zeros(2,3);A(:)=1:6;A=A*(1+i)A_A=A.'A_M=A'A=1.0000+1.0000i3.0000+3.0000i5.0000+5.0000i2.0000+2.0000i4.0000+4.0000i6.00
