MATLAB：一些杂例

a = 2; b = 5;
x = 0:pi/40:pi/2; %增量为pi/40
y = b*exp(-a*x).*sin(b*x).*(0.012*x.^4-0.15*x.^3+0.075*x.^2+2.5*x); %点乘的意义
z = y.^2; %点乘的意义
w(:,1) = x; %组成w，第一列为x
w(:,2) = y; %组成w，第二列为y
w(:,3) = z; %组成w，第三列为z
format short g; %短格式显示
w %不加分号，显示数据
%绘图显示，注意各种符号的属性设置
plot(x,y,'--rp','LineWidth',1.5,'MarkerSize',15,'MarkerEdgeColor','r','MarkerFaceColor','w');
hold on
plot(x,z,'b-s','MarkerEdgeColor','b','MarkerFaceColor','g');
legend('y关于x曲线','z关于y的曲线');

clc,clear;
q0 = 10; R = 60; C = 0.00005; t = linspace(0,0.8,100);
styleline = {'r-','b--','m:','c-.'};
leg = {};
i = 1; Qtl(1,:) = t;
for L = 3:3:12
    qt = q0*exp(-R*t/2/L).*cos(sqrt(1/L/C-(R/2/L)^2).*t);
    Qtl(i+1,:) = qt;
    plot(Qtl(1,:),Qtl(i+1,:),styleline{i});
    plot(t,qt,styleline{i},'LineWidth',2);
    leg{i} = strcat('L = ', num2str(L));
    i = i + 1;
    hold on
end
title('电量随时间的变化曲线'); 
legend(leg,'location','best'); 
xlabel('t(s)'); 
ylabel('q(t)'); 
grid on

%按要求处理第(1)步
x=0:pi/100:3*pi;
y=sin(x);
y1=(y>=0).*y; %消去负半波
p=sin(pi/3);
%按要求处理第(2)步
y2=(y>=p)*p+(y