Ploting A square around minima of a matrix

if we have minimum value of a matrix with the help of function min(mat). How we can plot a square around that minima of matrix. i would be very grateful if i got my answer as soon as possible

[Azzi Abdelmalek]

Dimension of your square?

Answer 1

[Azzi Abdelmalek]

a=1; % square dimension
mat=rand(5)
[c,idx]=min(mat(:))
[ii,jj]=ind2sub([5 5],idx)
x=[ii-a/2 ii+a/2 ii+a/2 ii-a/2 ii-a/2];
y=[jj-a/2 jj-a/2 jj+a/2 jj+a/2 jj-a/2];
plot(x,y,'r');hold on
plot(ii,jj,'o')
axis([ii-a ii+a jj-a jj+a])

Answer 2

[José-Luis]

x = rand(100,1);
y = rand(100,1)
[idx idx] = min(y);
plot(x,y,'.')
hold on;
plot(x(idx),y(idx),'s','MarkerSize',20) %Or whatever size you want

Answer 3

[Image Analyst]

Since you put image processing in your tags, I think you're looking for an image-based solution, so I offer up this demo. It generates a small sample image, then finds the min value and the (row,column) coordinates where the min(s) occur(s) (there may be more than 1 location where the min occurs for an integer image). Then for every location, it draws a box around that pixel, right at the interface/edge between one pixel and its neighbors. Just copy, paste, and run and you'll see.

clc;
close all;
clearvars;

% Generate a small sample image and display it (enlarged).
grayImage = randi(255, [30, 40])
imshow(grayImage, [], 'InitialMagnification', 800);
hold on;
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);

% Find the min value.
[minValue, minLinearIndex] = min(grayImage(:))

% Find out the rows and columns where it occurs.
% There may be more than 1!!!
[minRows minCols] = find(grayImage == minValue)

% For every min pixel found, plot a box around it.
lineWidth = 2;
for p = 1 : length(minRows)
  % Get the coordinates at the EDGES of the pixels.
  y1 = minRows(p)-0.5;
  y2 = minRows(p) + 0.5;
  x1 = minCols(p) - 0.5;
  x2 = minCols(p) + 0.5;
  % Get the vertices of a closed box around this point.
  % This will be 5 coordinates if the box is to be closed.
  boxX = [x1 x2 x2 x1 x1];
  boxY = [y1 y1 y2 y2 y1];
  % Now finally plot the box around this pixel.
  plot(boxX, boxY, 'r-', 'LineWidth', lineWidth);
end