# How can i connect the '.' points of the given figure. i don't want to connect '*' with any point?

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Lokesh Mangal on 7 Jan 2020
Answered: Asvin Kumar on 16 Jan 2020
%% Code that i used to creat that figure. %% I am trying to connect the dots to all nearby dots. %% To make 9 node element like as shown below. there will be Nx*Ny elements of this type.
clc ; clear;
% Dimensions of the plate
L = 1 ; % Length of the Plate along X-axes
B = 1 ; % Breadth of the Plate along Y-axes
% Number of Elements required
Nx = 3 ; % Number of Elements along X-axes
Ny = 3 ; % Number of Elements along Y-axes
%----------------------------------------
nel = Nx*Ny ; % Total Number of Elements in the Mesh
nnel = 9 ; % Number of nodes per Element
% Number of points on the Length and Breadth
npx = 2*Nx+1 ;
npy = 2*Ny+1 ;
nnode = npx*npy ;
nx = linspace(0,L,npx) ;
ny = linspace(0,B,npy) ;
[xx yy] = meshgrid(nx,ny) ;
% To get the Nodal Connectivity Matrix
coordinates = [xx(:) yy(:)] ;
NodeNo = 1:nnode ;
nodes = zeros(nel,nnel) ;
NodeNo = reshape(NodeNo,npx,npy);
%
nodes(:,1) = reshape(NodeNo(1:2:npx-2,1:2:npy-2),nel,1);
nodes(:,2) = reshape(NodeNo(3:2:npx,1:2:npy-2),nel,1);
nodes(:,3) = reshape(NodeNo(3:2:npx,3:2:npy),nel,1);
nodes(:,4) = reshape(NodeNo(1:2:npx-2,3:2:npy),nel,1);
nodes(:,5) = reshape(NodeNo(2:2:npx-1,1:2:npy-2),nel,1);
nodes(:,6) = reshape(NodeNo(3:2:npx,2:2:npy-1),nel,1);
nodes(:,7) = reshape(NodeNo(2:2:npx-1,3:2:npy),nel,1);
nodes(:,8) = reshape(NodeNo(1:2:npx-2,2:2:npy-1),nel,1);
nodes(:,9) = reshape(NodeNo(2:2:npx-1,2:2:npy-1),nel,1);
%%
X = zeros(nnel,nel) ;
Y = zeros(nnel,nel) ;
for iel = 1:nel
Y(:,iel) = coordinates(nodes(iel,:),1) ;
X(:,iel) = coordinates(nodes(iel,:),2) ;
end
x1 = X(1,:);
x2 = X(2,:);
x3 = X(3,:);
x4 = X(4,:);
x5 = X(5,:);
x6 = X(6,:);
x7 = X(7,:);
x8 = X(8,:);
x9 = X(9,:);
y1 = Y(1,:);
y2 = Y(2,:);
y3 = Y(3,:);
y4 = Y(4,:);
y5 = Y(5,:);
y6 = Y(6,:);
y7 = Y(7,:);
y8 = Y(8,:);
y9 = Y(9,:);
%%
figure
plot(x1,y1,'b.','MarkerSize',10)
xlim([-0.2 1.2])
ylim([-0.2 1.2])
hold on
plot(x2,y2,'b.','MarkerSize',10)
plot(x3,y3,'b.','MarkerSize',10)
plot(x4,y4,'b.','MarkerSize',10)
plot(x5,y5,'b.','MarkerSize',10)
plot(x6,y6,'b.','MarkerSize',10)
plot(x7,y7,'b.','MarkerSize',10)
plot(x8,y8,'b.','MarkerSize',10)
plot(x9,y9,'b*','MarkerSize',10)
hold off

Guillaume on 7 Jan 2020
In order to help we need the code that you used to create that figure (at least the line that plots the .)
Cam Salzberger on 7 Jan 2020
Also, are you trying to connect the dots to just one other dot, to all other dots, or all "nearby" dots (like "connect the dots")?

Asvin Kumar on 16 Jan 2020
Try using the following code to plot:
%% Plot
lw = 2; % LineWidth
ms = 15; % MarkerSize
figure
xlim([-0.2 1.2])
ylim([-0.2 1.2])
hold on
for i = 1:Nx
plot([x1(i) x4(end-Nx+i)],[y1(i) y4(end-Nx+i)],'k-','LineWidth',lw);
end
plot([x2(Nx) x3(end)],[y2(Nx) y3(end)],'k-','LineWidth',lw);
for i = 1:Ny
plot([x1(Nx*(i-1)+1) x2(i*Nx)],[y1(Nx*(i-1)+1) y2(i*Nx)],'k-','LineWidth',lw);
end
plot([x4(Nx*(Ny-1)+1) x3(end)],[y4(Nx*(Ny-1)+1) y3(end)],'k-','LineWidth',lw);
plot(x1,y1,'b.','MarkerSize',ms)
plot(x2,y2,'b.','MarkerSize',ms)
plot(x3,y3,'b.','MarkerSize',ms)
plot(x4,y4,'b.','MarkerSize',ms)
plot(x5,y5,'b.','MarkerSize',ms)
plot(x6,y6,'b.','MarkerSize',ms)
plot(x7,y7,'b.','MarkerSize',ms)
plot(x8,y8,'b.','MarkerSize',ms)
plot(x9,y9,'b*','MarkerSize',ms)
hold off
The expected output for Nx=3 and Ny=3 is:
If you want to display a grid, it will dpend on the XTick and YTick values. Have a look at those properties at: https://www.mathworks.com/help/matlab/ref/matlab.graphics.axis.axes-properties.html#budumk7-XTick