Storing a nodal points in cells based on the coordinates of the points

Having a set of nodal points with (x,y) coordinates. The goal is to store all the points in cells (cell 1, cell 2,...etc) variable based on their coordinates as shown in the figure below. The cells are numbered row by row as shown in figure.

The two variables below are required:

1- cellToNode{cellNo}(NoOfNodesInThisCell,1) : a Matlab cell that has all the nodes in each cell

2- nodeToCell(nodeNo,1) : a Matlab vector that has the cell no. containing a specific node

For example, When run in Matlab console: >> cellToNode{1}

The output is all nodes in cell 1

ans =

3

7

9

11

And when run, for exmaple: nodeToCell(1)

ans =

4

Since cell no. 1 has 4 nodes

Note: The set of nodes and cells in figure is just an example and the the real number of the points is large.

Answer 1

[Shubham Dhanda]

Hi, 

 

I understand that you want to display number of nodal points in each cell using nodeToCell variable and cell number of each nodal point in using cellToNode variable. From the information provided by you, I am assuming the nodal points and Grid Size.

 

nodalPoints = [3 1; 1 2; 2 2; 3 2; 2 3; 3 3; 1 4; 3 4; 2 5; 3 5];

gridSize = [3 3];

Below is the MATLAB code implementation of the problem:

% Define nodal points and grid size
nodalPoints = [3 1; 1 2; 2 2; 3 2; 2 3; 3 3; 1 4; 3 4; 2 5; 3 5];
gridSize = [3 3];

 

% Initialize variables
cellToNode = cell(prod(gridSize), 1);
nodeToCell = zeros(size(nodalPoints, 1), 1);

 

% Iterate over nodal points
for i = 1:size(nodalPoints, 1)
    x = nodalPoints(i, 1);
    y = nodalPoints(i, 2);

 

    % Determine which cell the nodal point belongs to
    cellX = ceil(x / gridSize(1));
    cellY = ceil(y / gridSize(2));
    cellNo = (cellY - 1) * gridSize(1) + cellX;

    % Add nodal point to cell
    cellToNode{cellNo} = [cellToNode{cellNo}; i];

    % Update nodeToCell variable
    nodeToCell(i) = cellNo;
end

 

% Display the nodal points in each cell
for i = 1:prod(gridSize)
    fprintf('Nodes in cell %d:\n', i);
    disp(cellToNode{i}');
end

Nodes in cell 1:

     1     2     3     4     5     6

Nodes in cell 2:
Nodes in cell 3:
Nodes in cell 4:

     7     8     9    10

Nodes in cell 5:
Nodes in cell 6:
Nodes in cell 7:
Nodes in cell 8:
Nodes in cell 9:

 

% Display the cell number for each nodal point
for i = 1:size(nodalPoints, 1)
    fprintf('Node %d in cell %d\n', i, nodeToCell(i));
end

Node 1 in cell 1
Node 2 in cell 1
Node 3 in cell 1
Node 4 in cell 1
Node 5 in cell 1
Node 6 in cell 1
Node 7 in cell 4
Node 8 in cell 4
Node 9 in cell 4
Node 10 in cell 4

[Dhafer Jadaan]

Thanks Shubham. You did not store the points based on their coordinates in each cell as I mentioned.

[Shubham Dhanda]

Hi Dhafer,

I have used sample data to solve the problem, you can change the nodalPoints based on your need to get the answer that you need. The idea was to tell you how you can solve your problem and I think you got it.