Why is my plot not showing?

a1 = 0; alpha1 = 0; d1 = 0;
a2 = 475; alpha2 = pi/2; d2 = 150;
a3 = 600; alpha3 = 0; d3 = 0;
%DH parameter
t1_min = -pi/2; t1_max = pi/2;
t2_min = -pi/3; t2_max = pi/3;
t3_min = -pi/3; t3_max = pi/3; 
% joint limits
% Monte Carlo method
% sampling size
N = 20000;
t1 = t1_min + (t1_max-t1_min)*rand(N,1);
t2 = t2_min + (t2_max-t2_min)*rand(N,1);
t3 = t3_min + (t3_max-t3_min)*rand(N,1);

function [ T ] = TranMat( a,b,c,d )
    T = [ cos(d) -sin(d)*cos(b)
    sin(d)*sin(b) a*cos(d); sin(d)
    cos(d)*cos(b) -cos(d)*sin(b) a*sin(d);
    0 sin(b) cos(b) c;
    0 0 0 1
     ];
    for i = 1:N
        A1 = TransMat(a1,alpha1,d1,t1(i));
        A2 = TransMat(a2,alpha2,d2,t2(i));
        A3 = TransMat(a3,alpha3,d3,t3(i));
        T = A1*A2*A3; 
        X=T(1,4);
        Y=T(2,4);
        Z=T(3,4);
        plot3(X,Y,Z,'.')
        hold on;
    end
end

Answer 1

[Geoff Hayes]

Tony - your code is not calling the TranMat function which has the code to plot the data. How should it be called? What do the a, b, c, and d input parameters correspond to in the script code?

[Tony Yu]

Thanks, it was a typo for "TransMat", and a, b,c,d are corresponded to a1,alpha1,d1,t1(i). I fixed the typo but the plot is still not showing. I don't see A1 to A3 show up in my workspace.

[Geoff Hayes]

But you are then calling TransMat from itself (is this intentional?)

    function [ T ] = TransMat( a,b,c,d )
        T = [ cos(d) -sin(d)*cos(b)
        sin(d)*sin(b) a*cos(d); sin(d)
        cos(d)*cos(b) -cos(d)*sin(b) a*sin(d);
        0 sin(b) cos(b) c;
        0 0 0 1
         ];
        for i = 1:N
            A1 = TransMat(a1,alpha1,d1,t1(i));
            A2 = TransMat(a2,alpha2,d2,t2(i));
            A3 = TransMat(a3,alpha3,d3,t3(i));
            T = A1*A2*A3; 
            X=T(1,4);
            Y=T(2,4);
            Z=T(3,4);
            plot3(X,Y,Z,'.')
            hold on;
        end
    end

How should it be called from the remainder of the code?

[Tony Yu]

clc;
clear all;
syms a b c d 
syms t1_min t2_min t3_min t4_min t5_min t6_min t7_min t1_max t2_max t3_max t4_max t5_max t6_max t7_max

a1 = 475; alpha1 = pi/2; d1 = 150;
a2 = 600; alpha2 = 0; d2 = 0;
a3 = 120; alpha3 = 0; d3 = 720;
%DH parameter
t1_min = -pi/2; t1_max = pi/2;
t2_min = -pi/3; t2_max = pi/3;
t3_min = -pi/3; t3_max = pi/3; 
% joint limits


% Monte Carlo method
% sampling size
N = 20000;
t1 = t1_min + (t1_max-t1_min)*rand(N,1);
t2 = t2_min + (t2_max-t2_min)*rand(N,1);
t3 = t3_min + (t3_max-t3_min)*rand(N,1);
for i = 1:N
    A1 = TransMat(a1,alpha1,d1,t1(i));
    A2 = TransMat(a2,alpha2,d2,t2(i));
    A3 = TransMat(a3,alpha3,d3,t3(i));
    T = A1*A2*A3; 
    X=T(1,4);
    Y=T(2,4);
    Z=T(3,4);
    plot3(X,Y,Z,'.')
    hold on;
end
figure(1)
view(3);
title('Isometric view');
xlabel('x (m)');
ylabel('y (m)');
zlabel('z (m) ');
figure(2)
view(2); % top view
title(' Top view');
xlabel('x (m)');
ylabel('y (m)');
figure(3)
view([1 0 0]); % y-z plane
title('Side view, Y-Z');
ylabel('y (m)');
zlabel('z (m)');
function T = TransMat(a,b,c,d)

T = [cos(d) -sin(d)*cos(b) sin(d)*sin(b) a*cos(d); sin(d) cos(d)*cos(b) -cos(d)*sin(b) a*sin(d); 0 sin(b) cos(b) c; 0 0 0 1];
end

I have fixed the code and it is working now, but now, figure 2 and figure 3 does not show anything

[Geoff Hayes]

But what should figure 2 and figure 3 show? There is no code to plot something to those figures as your for loop would only be plotting to the first figure.

[Tony Yu]

Is there a way to plot my for loop for the second figure and third figure with view(2) and view ([1 0 0])?

[Image Analyst]

Try not giving figure numbers as input, just accepting handles as outputs (if you even need to):

Instead of

figure(1)
figure(2)

do it like this:

h1 = figure;
h2 = figure;

etc.

[Geoff Hayes]

You could defer the plots until after the loop. Perhaps

N = 20000;
t1 = t1_min + (t1_max-t1_min)*rand(N,1);
t2 = t2_min + (t2_max-t2_min)*rand(N,1);
t3 = t3_min + (t3_max-t3_min)*rand(N,1);
X = zeros(N,1);  % <--- presize X,Y,Z
Y = zeros(N,1);
Z = zeros(N,1);
for i = 1:N
    A1 = TransMat(a1,alpha1,d1,t1(i));
    A2 = TransMat(a2,alpha2,d2,t2(i));
    A3 = TransMat(a3,alpha3,d3,t3(i));
    T = A1*A2*A3; 
    X(i)=T(1,4);
    Y(i)=T(2,4);
    Z(i)=T(3,4);
end
figure(1)
view(3);
title('Isometric view');
xlabel('x (m)');
ylabel('y (m)');
zlabel('z (m) ');
plot3(X,Y,Z,'.');     % <---- plot for figure 1
figure(2)
view(2); % top view
title(' Top view');
xlabel('x (m)');
ylabel('y (m)');
plot3(X,Y,Z,'.')     % <---- plot for figure 2
figure(3)
view([1 0 0]); % y-z plane
title('Side view, Y-Z');
ylabel('y (m)');
zlabel('z (m)');
plot3(X,Y,Z,'.')     % <---- plot for figure 3

I haven't tested the above but it might work...

[Tony Yu]

I tried your meathod but all 3 figures are showing view(3)...

[Tony Yu]

It works now, seems like it does not need to call out plot3 again on figure 2 and 3, thanks !