Creating a n*2 array from a variable in workspace

I have a variable on my workspace, in which i have n*2 elements ( 'n' rows and 2 columns). I wanna create an array to do some computation on all the elemental pairs of that variable, such that x1,y1... How can i do that ???

[madhan ravi]

x=data(:,1); % where data is the variable in the workspace
y=data(:,2);

[deep Dhillon]

Hi Madhan thanks for the reply though, but this actually creates another separate vector variable on my MAtlab workspace. What i essentially wanna do is to bring that matlab variable workspace into my command window and use those n*2 elemental pairs in the form of an array,, such that i would run an algorithm one by one each of the corrsponding x,y.

Here is an idea by what i mean

For

x1,y1 %use those points as an input and Run algo.

x2,y2 %use those points as an input and Run algo...

xn,yn %use those points as an input and Run algo

End

[madhan ravi]

for k=1:size(data,1)
    somefunction(data(k,:)) %like this ?
end

[deep Dhillon]

So i am using this function

evalin('base', 'centers')

This brings my variable 'centers' into the command window,, which has n*2 elements(please see the attached image)

What i wanna do is to use each of the values in that centers variable and use each of them to run an entire algorithm on those values. So essentially, with reference to the image.. i would run algorithm on 424.5621 212.4266 (which is like the pair x1,y1) and then algorithm on 551.959 376.5003 ... until algo. on 299.3605 509.6506 as such,, thus on each pair of the variable

Answer 1

[Image Analyst]

Try this and then adapt as needed:

% Creating bounding box at any given x,y
grayImage = imread('moon.tif');
[rows, columns, numberOfColorChannels] = size(grayImage)
imshow(grayImage);
boxHalfWidth = 40; %
xy = boxHalfWidth + rand(10, 2) * (rows - 2 * boxHalfWidth);
for k = 1 : size(xy, 1)
	x = xy(k, 1);
	y = xy(k, 2);
	hold on
	plot(x, y, 'r+', 'MarkerSize', 25)
	boxXStart = x-boxHalfWidth;
	boxYStart = y-boxHalfWidth;
	boxWidth = 2 * boxHalfWidth;
	boxHeight = 2 * boxHalfWidth;
	rectangle('Position',[boxXStart boxYStart boxWidth boxHeight], 'EdgeColor', 'r')
end

Answer 2

[Luna]

Please read this below:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

eval and evalin are not recommended. Why you are not just creating a function that gets your nx2 array as the input variable? And a for loop that gets your array's each row one by one?

For example:

function myOutputs = myAlgorithm(centers)
c = [];
for i = 1:size(centers,1)
    x = centers(i,1);
    y = centers(i,2);
    
    % do what you want with your x and y and then next iteration x and y will be your next row of your array
    c = [c x*y]; % just an example
end

myOutputs = c % just an example

end

[deep Dhillon]

Hi Luna

Thanks a lot for the reply

I tried couple of different ways, but i am not able to figure out precisely, how shall i write my function exactly. So indeed what i want to do is that to use all the x,y pairs of the centers variable (on my workspace, which is an n*2 array) and run the following algorithm to create the bounding boxes at those x,y coordinates.

% Creating bounding box at any given x,y
figure, imshow(mush);
hold on
x=425; % center location X
y= 211; % center location y
plot(centers)
boxHalfWidth = 40; %
boxXStart = x-boxHalfWidth;
boxYStart = y-boxHalfWidth;
boxWidth = 2 * boxHalfWidth;
boxHeight = 2 * boxHalfWidth;
rectangle('Position',[boxXStart boxYStart boxWidth boxHeight])

Essentially what i wanna do is that i should be able to input my function with the x,y and in turns it executes the above algorithm for each x,y pair in my center variable

Answer 3

[deep Dhillon]

Image analyst

It works really well, onto my application.

Greatly appreciate you for the support