is there a way to make matrices out of a bigger matrix with a changing condition without using a loop

so i have the points of a field in a 2D matrix and a line is cutting that field , i want to take only points which are below the field . is there a way for me to put some condition when i make another matrix from the field such that i only consider the points below that field without using any loop ?

using a loop will make my code very heavy and hence i want to avoid that .

[KSSV]

Yes this can be achieved with out loop. You need to give more info and a pictorial example will help us to help you.

Answer 1

[Rohit Kulkarni]

Hi Kashish,

I understand that you have a matrix and a line cut through it, and you would like to obtain the points which are below the line without using a for loop.

The points below the line can be filtered by using logical indexing and matrix operations.

The general approach is:

• Define line equation.
• Create logical mask and use it to identify points below the line equation.

The following code snippet shows an example of this:

% Define the parameters of the line equation: y = mx + b.
m = 0.5;  % Slope of the line
b = 10;   % Y-intercept of the line

% Create a 2D matrix representing your field (random data in this case).
% Replace this with your actual data.
fieldSize = 100;
fieldMatrix = rand(fieldSize, fieldSize) * 100;

% Create an array of x-coordinates corresponding to the columns of the matrix.
xCoordinates = 1:fieldSize;

% Create a matrix of y-coordinates based on the line equation.
yCoordinates = m * xCoordinates + b;

% Create a logical mask to identify points below the line.
mask = (1:fieldSize)' > yCoordinates;

% Extract the points below the field using the logical mask.
pointsBelowField = fieldMatrix;
pointsBelowField(mask) = NaN;  % Set points above the line to NaN

% Create a matrix of values for the points above the line.
pointsAboveField = fieldMatrix;
pointsAboveField(~mask) = NaN;  % Set points below the line to NaN

% Display both matrices
figure;

% Display the points below the line
subplot(1, 2, 1);
imagesc(pointsBelowField);
colormap('jet');
title('Points Below Line');
colorbar;

% Display the points above the line
subplot(1, 2, 2);
imagesc(pointsAboveField);
colormap('jet');
title('Points Above Line');
colorbar;

% Display both plots side by side
sgtitle('Points Above and Below Line');

Hope it resolves your query!