end-10, end 【例41-3】已知x=sin d 函数在区间[0,2z]中的 098 0.97 d=pi/100;t=0:d:2pi; x=sin(t); 096 dxdt diff=diff(x)/d; 0950 ○ddt dxdt grad=gradient(x)/d; subplot(1, 2, 1); plot(t, x, b); hold on plot(t, dxdt grad, 'm, Line Width, 8) 宏观上, difffigradient结果大致相同 plot(t(1: end-1), dxdt diff, k, Marker Size, 8) axis([0, 2*pi, 1.1, 1.1 D; title( 0, 2\pi) legend(x(t),dxdt grad , dxdt diff, Location, North) xlabel('t), box off; hold off subplot(1, 2, 2) 细节上, diffFHgradient数值有差异, kk(length(t)-10):length(t); df没有给出最后一点导数 hold on; plot(t(kk), dxdt grad(kk),om, MarkerSize, 8) plot(t(kk-1), dxdt diff(kk-1), k, Marker Size, 8) titleflend-10, end) legend(dxdt grad ,dxdt diff, Location, South East) xlabel('t), box off; hold off 页2021/1/26 第8页 d=pi/100; t=0:d:2*pi; x=sin(t); dxdt_diff=diff(x)/d; dxdt_grad=gradient(x)/d; 【例4.1-3】已知 采用diff和gradient计算该 函数在区间 中的近似导函数。 x = sin( t) [0, 2 ] subplot(1,2,1); plot(t,x,'b');hold on plot(t,dxdt_grad,'m','LineWidth',8) plot(t(1:end-1),dxdt_diff,'.k','MarkerSize',8) axis([0,2*pi,-1.1,1.1]); title('[0, 2\pi]') legend('x(t)','dxdt_{grad}','dxdt_{diff}','Location','North') xlabel('t'), box off;hold off subplot(1,2,2) kk=(length(t)-10):length(t); hold on; plot(t(kk),dxdt_grad(kk),'om','MarkerSize',8) plot(t(kk-1),dxdt_diff(kk-1),'.k','MarkerSize',8) title('[end-10, end]') legend('dxdt_{grad}','dxdt_{diff}','Location','SouthEast') xlabel('t'),box off; hold off 宏观上, diff和gradient结果大致相同 细节上, diff和gradient数值有差异， diff没有给出最后一点导数