Z must be a matrix, not a scalar or vector

clc
clear all
R=10;
f=0.5;
s=50;
N=36;
a=f/(s*N);
Ax=0.002;
Ay=0.002;
lx=2.5;
ly=2.5;
n=((R*s*N)/f)+1;
for i=1:n
r(i)=(R-((i-1)*a));
theta(i)= ((i-1)*(2*pi/N));
x(i)=(r(i)*cos(theta(i)));
y(i)=(r(i)*sin(theta(i)));
[xx(i),yy(i)]=meshgrid(x(i),y(i));
Z(i)=((Ax*cos(2*pi*xx(i)/lx))+(Ay*cos(2*pi*yy(i)/ly)));
end
surf(xx,yy,Z);

[Yazan]

You forgot to ask a question.

[Kundan Prasad]

I want 3d plot and every time i am getting an error that Z must be a matrix, not a scalar or vector

Answer 1

[Matt J]

R=10;
f=0.5;
s=50;
N=36;
a=f/(s*N);
Ax=0.002;
Ay=0.002;
lx=2.5;
ly=2.5;
n=((R*s*N)/f)+1;
for i=1:n
r(i)=(R-((i-1)*a));
theta(i)= ((i-1)*(2*pi/N));
x(i)=(r(i)*cos(theta(i)));
y(i)=(r(i)*sin(theta(i)));
% [xx(i),yy(i)]=meshgrid(x(i),y(i));
Z(i)=((Ax*cos(2*pi*x(i)/lx))+(Ay*cos(2*pi*y(i)/ly)));
end


T=delaunayTriangulation(x(:),y(:));
 trisurf(T.ConnectivityList,x(:),y(:),Z(:),'EdgeColor','none','FaceAlpha',0.6);
 view(-80,75)

[Kundan Prasad]

Thank you but can we change Triangulation to other form so that smooth profile can be obtained

[Matt J]

To get a smoother profile, increase the number of samples (e.g., with N=360):

R=10;
f=0.5;
s=50;
N=360;

....

T=delaunayTriangulation(x(:),y(:));
 trisurf(T.ConnectivityList,x(:),y(:),Z(:),'EdgeColor','none','FaceAlpha',0.6);
 view(-80,75)

[Kundan Prasad]

thank you it worked

[Matt J]

You're welcome, but please Accept-click the answer to indicate that it worked.

Answer 2

[Kundan Prasad]

R=10;
f=0.5;
s=50;
N=100;
a=f/(s*N);
Ax=2;
Ay=2;
lx=2.5;
ly=2.5;
n=((R*s*N)/f)+1;
r(0)=0;
Z(0)=0;
t=0.5;
for i=1:n   
r(i)=(R-((i-1)*a));
theta(i)= ((i-1)*(2*pi/N));
x(i)=(r(i)*cos(theta(i)));
y(i)=(r(i)*sin(theta(i)));
Z(i)=((Ax*cos(2*pi*x(i)/lx))+(Ay*cos(2*pi*y(i)/ly)));
m(i) = ((Z(i-1) - Z(i))./(r(i-1)-r(i)));
newth(i) = atan(-m(i));
G(i)=r(i)-(t*sin(newth(i)));
H(i)=Z(i)+(t*cos(newth(i)))-t; %% THE compensate value of r1 and Z1
                                  % needed to calculate from the previous value of r(i) and Z(i)
end
T=delaunayTriangulation(x(:),y(:));
 trisurf(T.ConnectivityList,x(:),y(:),Z(:),'EdgeColor','none','FaceAlpha',0.6);
 view(-80,75)

I am unable to calculate the value of G and H from the previous value of r(i) and Z(i). Can you please check the code. Thank you

[Walter Roberson]

r(0)=0;

Array indices must be positive integers or logical values.

Z(0)=0;

[Kundan Prasad]

Exactly i am also getting the same statement. Actual from r(i) and Z(i), I have to calculate the G and H. r(0)=0 and Z(0)=0, I have randomly initilize. For calculation of slope i.e. m(1)= Z(2)-Z(1)/r(2)-r(1), I need to call the value of r(2) and r(1) from r(i) and same in case of Z(i). I am unable to call this value.

[Walter Roberson]

The only part of MATLAB that is able to use indices starting from zero, is Simulink (and maybe Symbolic Toolbox if I dug deeply enough.)

In any case where you have an array being indexed starting from integer S and S < 1 then you need to add (1-S) to each array index expression. For example if your array indices started from -2 then you would have to add (1-(-2)) = 3 to each index expression.

roff = 1;
Zoff = 1;
r(0+roff)=0;
Z(0+Zoff)=0;
t=0.5;
for i=1:n   
r(i+roff)=(R-((i-1)*a));
theta(i)= ((i-1)*(2*pi/N));
x(i)=(r(i+roff)*cos(theta(i)));
y(i)=(r(i+roff)*sin(theta(i)));
Z(i)=((Ax*cos(2*pi*x(i)/lx))+(Ay*cos(2*pi*y(i)/ly)));
m(i) = ((Z(i-1+Zoff) - Z(i))./(r(i-1)-r(i+roff)));
newth(i) = atan(-m(i));
G(i)=r(i+roff)-(t*sin(newth(i)));
H(i)=Z(i+Zoff)+(t*cos(newth(i)))-t; %% THE compensate value of r1 and Z1
                                  % needed to calculate from the previous value of r(i) and Z(i)
end

[Kundan Prasad]

Still same error is showing

Array indices must be positive integers or logical values.

Error in thert1 (line 22)

m(i) = ((Z(i-1+Zoff) - Z(i))./(r(i-1)-r(i+roff)));

[Walter Roberson]

R=10;
f=0.5;
s=50;
N=100;
a=f/(s*N);
Ax=2;
Ay=2;
lx=2.5;
ly=2.5;
n=((R*s*N)/f)+1;

roff = 1;
Zoff = 1;
r(0+roff)=0;
Z(0+Zoff)=0;
t=0.5;
for i=1:n   
    r(i+roff)=(R-((i-1)*a));
    theta(i)= ((i-1)*(2*pi/N));
    x(i)=(r(i+roff)*cos(theta(i)));
    y(i)=(r(i+roff)*sin(theta(i)));
    Z(i+Zoff)=((Ax*cos(2*pi*x(i)/lx))+(Ay*cos(2*pi*y(i)/ly)));
    m(i) = ((Z(i-1+Zoff) - Z(i))./(r(i-1+roff)-r(i+roff)));
    newth(i) = atan(-m(i));
    G(i)=r(i+roff)-(t*sin(newth(i)));
    H(i)=Z(i+Zoff)+(t*cos(newth(i)))-t; %% THE compensate value of r1 and Z1
                                      % needed to calculate from the previous value of r(i) and Z(i)
end

size(H)

ans = 1×2

1 100001

[Kundan Prasad]

R=10;
f=0.5;
s=50;
N=100;
a=f/(s*N);
Ax=2;
Ay=2;
lx=2.5;
ly=2.5;
n=((R*s*N)/f)+1;
roff = 1;
Zoff = 1;
r(0+roff)=0;
Z(0+Zoff)=0;
t=0.1;
for i=1:n   
    r(i+roff)=(R-((i-1)*a));
    theta(i)= ((i-1)*(2*pi/N));
    x(i)=(r(i+roff)*cos(theta(i)));
    y(i)=(r(i+roff)*sin(theta(i)));
    Z(i+Zoff)=((Ax*cos(2*pi*x(i)/lx))+(Ay*cos(2*pi*y(i)/ly)));
    m(i) = ((Z(i-1+Zoff) - Z(i))./(r(i-1+roff)-r(i+roff)));
    newth(i) = atan(-m(i));
    G(i)=r(i+roff)-(t*sin(newth(i)));
    H(i)=Z(i+Zoff)+(t*cos(newth(i)))-t; %% THE compensate value of G and H
                                      % needed to calculate from the previous value of r(i) and Z(i)
end
size(H)
T=delaunayTriangulation(x(:),y(:));
 trisurf(T.ConnectivityList,x(:),y(:),H(:),'EdgeColor','none','FaceAlpha',0.6);
 view(-80,75)

It is working but i am not getting the desired value. The value of r(i) and G are same and same case for Z(i) and H. For example if the value of r(1)=1 and Z(1)=4, then after giving the compensation value t=0.1, the new value i.e. G(1) and H(1) should be different from the r(1) and Z(1). Can you please enlighted how to solve this issue. Thank you

[Walter Roberson]

No, r(1) needs to be used to store the initial value, r(0+roff) and Z(1) needs to be used to store the initial value Z(0+Zoff) . The first output value is at r(1+roff) and Z(1+zoff)

[Kundan Prasad]

Still same value for both i.e. r(i) and G is showing

[Walter Roberson]

R=10;
f=0.5;
s=50;
N=100;
a=f/(s*N);
Ax=2;
Ay=2;
lx=2.5;
ly=2.5;
n=((R*s*N)/f)+1;
roff = 1;
Zoff = 1;
r(0+roff)=0;
Z(0+Zoff)=0;
t=0.1;
Pi = (pi);
for i=1:n   
    r(i+roff)=(R-((i-1)*a));
    theta(i)= ((i-1)*(2*Pi/N));
    x(i)=(r(i+roff)*cos(theta(i)));
    y(i)=(r(i+roff)*sin(theta(i)));
    Z(i+Zoff)=((Ax*cos(2*Pi*x(i)/lx))+(Ay*cos(2*Pi*y(i)/ly)));
    m(i) = ((Z(i-1+Zoff) - Z(i+Zoff))./(r(i-1+roff)-r(i+roff)));
    newth(i) = atan(-m(i));
    G(i)=r(i+roff)-(t*sin(newth(i)));
    H(i)=Z(i+Zoff)+(t*cos(newth(i)))-t; %% THE compensate value of G and H
                                      % needed to calculate from the previous value of r(i) and Z(i)
end

T=delaunayTriangulation(x(:),y(:));
 trisurf(T.ConnectivityList,x(:),y(:),H(:),'EdgeColor','none','FaceAlpha',0.6);
 view(-80,75)

[Kundan Prasad]

Thank you, now its working