想通过plot模拟四连杆运动，但是不会删除之前的线怎么办？

felton

% D- ?/ o- j8 i. I8 L1 {7 `# M想通过plot模拟四连杆运动，
但是不会删除之前的线，
' F% i( \% ^, c9 K* V; V' ?% j最后所有线的轨迹都在上面，
( L/ [( E& p5 H# c% `请教大神怎么可以删除？非常感谢！
9 K$ w) Q  e* \8 H8 k. K7 g6 Z% |clc
: H+ e0 j2 t; j2 m4 l3 M; n6 v# {/ \a=100;
  j, M3 K, w# j2 |b=350;
1 u+ y' h2 r. W) }: N+ i  D" ec=300;
d=400;
# ?" y* {: u8 A/ Asyms t0;
syms t1;
  p' x. ~" M7 {8 C% ]syms t2;
A=2*c*d-2*a*c*cos(t0);
$ c# Z# b8 ]; k/ K+ gB=2*a*c*sin(t0);
C=c^2+a^2+d^2-b^2-2*a*d*cos(t0);
! h- C. ?4 |+ [- C/ Y9 f1 ht1=2*atan((B-sqrt(B^2-C^2+A^2))/(C-A));
* ]9 x% b$ P$ hfigure;
! G8 q) l1 A# s; r1 M" Z7 G& dsyms xa xb xc xd ya yb yc yd;
+ I8 {# v0 T8 f* et0=0:0.1:2*pi;
D=2*b*d-2*a*b*cos(t0);
, L0 a3 A1 Y$ ]& L! j. bE=-2*a*b*sin(t0);
( @* F, {' A4 E* W$ r1 M5 ZF=a^2+b^2-c^2+d^2-2*a*d*cos(t0);
& L4 d& C% `. B/ _. `t2=2*atan((E+sqrt(D.^2+E.^2-F.^2))./(D+F));
xa=0;
' S2 q4 w  C- }8 U5 s: Rya=0;
$ r5 r9 N- ~2 ~1 g; X) {6 r& [8 cxb=a*cos(t0);
yb=a*sin(t0);
- e# n7 v0 l: t4 txc=xb+b*cos(t2);
yc=yb+b*sin(t2);
xd=d;
7 C; J' {; a  z* G9 t; Z1 Hyd=0;
, R% t  o. }# v! F$ KAB=line([xa,xb(1)],[ya,yb(1)]);
( V6 a" y* t4 h, R  y* pBC=line([xb(1),xc(1)],[yb(1),yc(1)]);
CD=line([xc(1),xd],[yc(1),yd]);
AD=line([xa,xd],[ya,yd]);
8 F- n: u& n# I8 c7 T8 Q8 e+ ~for i=1:length(xb)
    plot([xa,xb(i)],[ya,yb(i)]),hold on;
    plot([xb(i),xc(i)],[yb(i),yc(i)]),hold on;
+ D( u3 P. g, o5 ?5 ]    plot([xc(i),xd],[yc(i),yd]),hold on;
/ v" r" H" ^" C9 o9 }7 E0 v- P" Y    plot([xa,xd],[ya,yd]),hold on;
    drawnow
    pause(0.1)
  f& e9 x& @/ o0 W" m4 Eend

Allevi

配合clf函数
Xmin = min([xa xb xc xd]); Xmax =  max([xa xb xc xd]);
1 h  x9 j4 Z: q5 B% tYmin = min([ya yb yc yd]); Ymax =  max([ya yb yc yd]);
! j0 w0 b# o: L1 }7 }( H- ^4 Mfor i=1:length(xb)
2 |. i3 @) L. l" L# o    clf;   
    plot([xa,xb(i)],[ya,yb(i)],'k');
9 C; G5 P: W$ n2 W+ U; G    xlim([Xmin Xmax]); ylim([Ymin Ymax]);hold on;
; `0 B% o9 `# r2 |' C1 M* }& m    plot([xb(i),xc(i)],[yb(i),yc(i)],'r');
1 k/ @3 x0 W2 v5 b    plot([xc(i),xd],[yc(i),yd],'b');
0 c1 u$ K3 D  d9 K8 S9 f' w1 L. S7 Q4 x    plot([xa,xd],[ya,yd],'m');
    drawnow
    pause(0.1)
- j# R6 K8 {# g5 q: c. Xend