Why is nothing showing up on my plots?

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Jade Cruz
Jade Cruz 2023-7-5
回答： Star Strider 2023-7-5
All three plots won't show the iterations from my calculation.
% Simulate the system
for k = 1:(tf - t0)/dt
% Update the reference joint positions
q_r = q + dt*qdr;
% Calculate the Jacobian
J = calc_jacobian(q, L1, L2, L3);
% Update the actual joint positions
q = q_r + dt*J'*qdr;
% Plot the results
if k == 1
plot_results(q, J);
end
end
function plot_results(q, J)
% Plot the joint positions
subplot(3, 1, 1)
hold on
plot(q(1), 'b')
plot(q(2), 'r')
plot(q(3), 'g')
xlabel('Time (s)')
ylabel('Joint angle (deg)')
% Plot the Jacobian determinant
subplot(3, 1, 2)
plot(J'*J)
xlabel('Time (s)')
ylabel('Jacobian determinant')
% Plot the end-effector pose
subplot(3, 1, 3)
plot(q(1), q(2), 'b*')
xlabel('x (m)')
ylabel('y (m)')
axis([-2, 4, -2, 4])
end
  9 个评论
显示 7更早的评论
Sandeep Mishra
Sandeep Mishra 2023-7-5
I have answered that for example case with 3 different figures.
If you still face any error, do comment
Jade Cruz
Jade Cruz 2023-7-5
@Sandeep Mishra Thank you for your help! I have posted a comment below your answer. I appreciate the continuous support.

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回答（3 个）

Steven Lord
Steven Lord 2023-7-5
Ran in:
When you call plot with just a color in the line specification, what you get is a plot with no markers.
h = plot(1, 'b');
h.Marker
ans = 'none'
What does a line "connecting" one point look like? Nothing. If instead you'd specified a marker in addition to a color, you'd get a line "connecting" one point and a marker on that point.
figure
h = plot(1, 'bx');
If you want to create a plot where you add points to a line iteratively, I'd use the animatedline function to create the line then call addpoints on the animated line. You won't be able to see the iterative process in Answers, but if you run the code below in an interactive session of MATLAB you'll see the plot appear, point by point.
x = 0:360;
y = sind(x);
figure
axis([0 360 -1 1])
h = animatedline('LineStyle', '-', 'Color', 'b');
for k = 1:numel(x)
addpoints(h, x(k), y(k))
pause(1/32)
end
Sandeep Mishra
Sandeep Mishra 2023-7-5
编辑：Torsten 2023-7-5
Ran in:
Hello Jade,
I understood from our discussion in the comments that you are trying to plot multiple plots (in your case = 50)
In MATLAB, you can use figure(n) to create a figure with number property is equal to n.
You can refer the below example code (plot with 3 figures)
clear;
% Define the parameters
L1 = 4;
L2 = 3;
L3 = 2;
dt = 0.1;
t0 = 0;
tf = 5;
q0 = [10, 20, 30]';
qdr = [0.2, -0.3, -0.2]';
% Initialize the variables
q = q0;
J = zeros(3, 3);
% for k = 1:(tf - t0)/dt
% Example
for k = 1:3
% Update the reference joint positions
q_r = q + dt*qdr;
% Calculate the Jacobian
J = calc_jacobian(q, L1, L2, L3)
% Update the actual joint positions
q = q_r + dt*J'*qdr
% Plot the results
figure(k)
plot_results(q, J);
end
J = 3×1
5.7498 -4.7984 1.0000
q = 3×1
10.2589 20.2089 30.2189
J = 3×1
7.0790 -2.0237 1.0000
q = 3×1
10.4612 20.3612 30.3812
J = 3×1
7.1168 0.3353 1.0000
q = 3×1
10.5935 20.4435 30.4735
function J = calc_jacobian(q,L1,L2,L3)
% Calculate the Jacobian
J = [-L1*sin(q(1)) - L2*sin(q(1) + q(2)) - L3*sin(q(1) + q(2) + q(3));
L1*cos(q(1)) + L2*cos(q(1) + q(2)) + L3*cos(q(1) + q(2) + q(3));
1];
end
function plot_results(q, J)
% Plot the joint positions
subplot(3, 1, 1)
hold on
plot(q(1), 'b')
plot(q(2), 'r')
plot(q(3), 'g')
xlabel('Time (s)')
ylabel('Joint angle (deg)')
% Plot the Jacobian determinant
subplot(3, 1, 2)
plot(J'*J)
xlabel('Time (s)')
ylabel('Jacobian determinant')
% Plot the end-effector pose
subplot(3, 1, 3)
plot(q(1), q(2), 'b*')
xlabel('x (m)')
ylabel('y (m)')
axis([-2, 4, -2, 4])
end
You can refer to the below documentation to learn more about "figure" in MATLAB.
https://in.mathworks.com/help/matlab/ref/figure.html#d124e460113
  2 个评论
Jade Cruz
Jade Cruz 2023-7-5
编辑：Jade Cruz 2023-7-5
That is perfect but I do notice that all the figures do not show any sort of information or plot. Would the problem be my equations and not my code?

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Star Strider
Star Strider 2023-7-5
Ran in:
It now fills the matrices corrrectly and plots something, however I cannot determine what you want it to plot —
% Regarding the missing values:
% Define the parameters
L1 = 4;
L2 = 3;
L3 = 2;
dt = 0.1;
t0 = 0;
tf = 5;
q0 = [10, 20, 30]';
qdr = [0.2, -0.3, -0.2]';
% Initialize the variables
q(:,1) = q0;
J = zeros(3, 3);
kv = 1:(tf - t0)/dt; % Create Vector
for k = 1:numel(kv)
% Update the reference joint positions
q_r(:,k+1) = q(:,k) + dt*qdr; % Subscript Result (Create Matrix Of Column Vectors)
% Calculate the Jacobian
J(:,k+1) = calc_jacobian(q(:,k), L1, L2, L3); % Subscript Result (Create Matrix Of Column Vectors)
% Update the actual joint positions
q(:,k+1) = q_r(:,k) + dt*J(:,k)'*qdr; % Subscript Result (Create Matrix Of Column Vectors)
end
% Plot the results
figure
plot(q, J)
grid
xlabel('q')
ylabel('J')
title('Original Matrices')
figure
plot(q.', J.')
grid
xlabel('q')
ylabel('J')
title('Transposed Matrices')
function J = calc_jacobian(q,L1,L2,L3)
% Calculate the Jacobian
J = [-L1*sin(q(1)) - L2*sin(q(1) + q(2)) - L3*sin(q(1) + q(2) + q(3));
L1*cos(q(1)) + L2*cos(q(1) + q(2)) + L3*cos(q(1) + q(2) + q(3));
1];
end
I defer to you to figure out how to plot the results.
.

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