How to obtain values from a table in matlab

I have a table with two columns as circle's centre position and third one with frame number 1-1000. I want to obtain the values of circle centres in frame n and n-1 at a time, inorder to make matrix out of it

How can I do that?

Answer 1

[Adam Danz]

I'm not sure what you mean by "in order to make a matrix out of it". If this demo doesn't address the problem, please provide an example. Otherwise, here's how to extract the (x,y) coordinates for a given frame.

%Fake data
T = table((1:9)',(2:10)',[1;1;1;2;2;2;3;3;3],'VariableNames',{'X','Y','Frame'}); 

f = 2;                         	% frame number 
frameIdx = T.Frame == f;    	        %row numbers of frame n
frameIdx = T.Frame == f-1;    	%row numbers of frame n-1 (not used in this demo)

% FROM HERE YOU CAN DO LOTS OF THINGS LIKE...

% ...isolate rows of table that belong to frame n
T(frameIdx,:)

% ...isolate only the (X,Y) values that belong to frame n
T(frameIdx,{'X','Y'})

% ...put (X,Y) values from frame n into a matrix
T{frameIdx,{'X','Y'}}

I recommend keeping the data in the table rather than extracting it into a matrix unless your analysis requres a matrix.

[karishma koshy]

Im actually trying to do munkres Hungarian algorithm. So I want to find the position difference of a particular circle from one frame to another frame. The circle represents the bacteria, and it's actually moving.

How can I find the distance between points.

[Adam Danz]

"How can I find the distance between points."

Distance = sqrt((x2-x1)^2 + (y2-y1)^2)

Thanks to Pythagoras.

(x1,y1) are the coordinates at frame n; (x2,y2) are coordinates at frame n-1 (or the other way around; it doesn't matter).

[karishma koshy]

 Dear sir 
Can you help me construct a for loop to find the distance  between loops in n and n-1 frames and terminate the loop when it's reached the last value of both the frames

[Adam Danz]

The loop will probably look something like this; T is your table.

% Create fake data
T = table((1:9)',(2:10)',[1;1;1;2;2;2;3;3;3],'VariableNames',{'X','Y','Frame'}); 

n = size(T,1)';   %number of rows in your table
distFcn = @(x1,x2,y1,y2)sqrt((x2-x1)^2 + (y2-y1)^2);  %distance function

% Loop through each row starting at row #2
d = zeros(n-1,1);  %create a vector where the distances will be stored
for i = 2:n
    d(i-1) = distFcn(T.X(i-1),T.X(i),T.Y(i-1),T.Y(i));
end

And you can do that without a loop, too.

distFcn = @(x1,x2,y1,y2)sqrt((x2-x1).^2 + (y2-y1).^2);  %distance function
%                                   ^            ^   note the dots
d = distFcn(T.X(2:end),T.X(1:end-1),T.Y(2:end),T.Y(1:end-1))

[karishma koshy]

Dear Sir I'm aiming to measure the distance between all points in one frame and all points in the next frame. So I want to

Create a table (let’s call this “table i”)which only contains points in frame i (where “i" is the index of that frame) Create another table (“table i+1”), which only contains points in frame i+1 Create a 2D distance matrix (width equal to the number of points in frame i and height equal to the number of points in frame i+1) where each element is the Pythagoras distance between two points.

How can I implement this as a code ? Thank you