# Robot not being plotted on 3D

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Mohsina Zafar on 6 Jan 2019
Commented: Jubil Mahadevan on 19 Jan 2020
Hello,
I want to plot a robot but it is not coming to be. A 2-D plane is being generated instead of 3D space. Attached is the code of robot. Please guide in this regard.
syms q1 q2 q4 a1 a2 d3 d4 t
%q1,q2,d3,q4 variable angle
% a1 a2 , d4 length robot
assume(a1,'real');assume(a1>0);
assume(a2,'real');assume(a2>0);
assume(d3,'real');assume(d3>0);
assume(d4,'real');assume(d4>0);
assume(q1,'real');
assume(q2,'real');
assume(q4,'real');
%INPUT MATRIX DEVAVIT HARTENBERG
A_01=[cos(q1) -sin(q1) 0 a1*cos(q1); sin(q1) cos(q1) 0 a1*sin(q1); 0 0 1 0; 0 0 0 1];
A_12=[cos(q2) sin(q2) 0 a2*cos(q2); sin(q2) -cos(q2) 0 a2*sin(q2); 0 0 -1 0; 0 0 0 1];
A_23=[1 0 0 0; 0 1 0 0; 0 0 1 d3; 0 0 0 1];
A_34=[cos(q4) -sin(q4) 0 0; sin(q4) cos(q4) 0 0; 0 0 1 d4; 0 0 0 1];
%MATRIX LAST DENAVIT HARTENBERG
A_04=A_01*A_12*A_23*A_34;
A_02=simplify(A_01*A_12);
A_03=simplify(A_02*A_23);
disp('MATRIX LAST')
A_04=simplify(A_04)
rE=A_04(1:3,4) % FINAL POINT FOR ACTIVITIES
%ROBOTICS SYSTEM TOOLBOX-PEER CORKE
L(3).qlim=[0,0.3];
t=[0:0.005:4];
j=length(t);
for i=1:j
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
xE(i)= 0.3+0.2*(1+sin(5*t(i))*cos(t(i)));
yE(i)= 0.3+0.2*(1+sin(5*t(i))*sin(t(i)));
zE(i)=-0.3;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
A=xE(i);
B=yE(i);
D=-0.4^2+xE(i).^2+yE(i).^2+0.5^2;
s1=(D.*B-A.*sqrt(A.^2+B.^2-D.^2))./(A.^2+B.^2);
c1=(D.*A+B.*sqrt(A.^2+B.^2-D.^2))./(A.^2+B.^2);
q1_num(:,i) = atan2(s1,c1);
s2= (yE(i) -0.5.*sin(q1_num(:,i)));
c2= (xE(i) -0.5.*cos(q1_num(:,i)));
q2_num(:,i)= atan2(s2,c2)-q1_num(:,i);
d3_num(:,i) = -zE(i)-0.1;
q4_num(:,1)= q1_num(:,i)+q2_num(:,i);
end
figure
clf
hold on
grid on
axis([-1,1,-1,1,-1,1])
for i=1:length(t)
plot(rob,[q1_num(1,i),q2_num(1,i),d3_num(1,i),q4_num(1,i)])
plot3(xE(i),yE(i),zE(i),'b.')
pause(1/1000) %video
end
The error I get is in this line:
plot(rob,[q1_num(1,i),q2_num(1,i),d3_num(1,i),q4_num(1,i)])
Error:
Index exceeds matrix dimensions.
d = norm( d(4:6)-d(1:3) ) / 72;
handle = create_robot(robot, opt);
P.S: I am using robotics toolbox by Pete Corke.

Walter Roberson on 6 Jan 2019
hold on
grid on
axis([-1,1,-1,1,-1,1])
You had not plotted anything to that axis before that point. It defaulted to 2D. The "hold on" freezes that current view by default, so even though you pass in a 3D view to axis(), if you were to call axis() it would return only a 2D view. This matters because the SerialLink plot routine assumes you are in a 3D view.
The cure is to call view(3) before hold on