How to find a structure point with two fields x and y and then find the distance between two points

I am lost how to create a structure point so I use it two create two points and then find the distance between these two points.

The instructions that was given to me was:

Define a structure point containing two fields, x and y. The x field will contain the x-position of the point, and the y field will contain the y-position of the point. Then write a function dist3 that accepts two points and returns the distance between the two points on the Cartesian plane. Be sure to check the number of input arguments in your function.

Here is what I have so far.

 function [ out ] = pointDist3( varargin )
  %FUNCTION pointDist3 takes in any two pairs of points and 
  % Calling sequence:
  %   out = pointDist3(varargin)
  %DEFINE VARIABLES
  % minargs, maxargs = error checking variables 

minargs = 4; 
maxargs=8;
nargchkin(minargs,maxargs); 

%Initalize values
jj = 0;
linespec = '';
    % Get the x and y values, making sure to save the line
% specification string, if one exists.
    for ii = 1:nargin
        % Is this argument an [x,y] pair or the line
        % specification?
        if ischar(varargin{ii})
        % Save line specification
         linespec = varargin{ii};
        else
    % This is an [x,y] pair. Recover the values.
        jj = jj + 1;
        x(jj) = varargin{ii}(1);
        y(jj) = varargin{ii}(2);
        end
    end
% Plot
end

Answer 1

[Geoff Hayes]

Iris - I think the first step is to define the point structure/object as something like

 pointA.x = 12;
 pointA.y = 32;

which would represent the point (12,32) in the 2D Cartesian plane, with x and y being your two fields. Your distance function, dist3, would take two of these structures as its inputs, and you would then calculate the distance between the two points.

Since this is a homework assignment, try to incorporate the above into your code. When you review your updated function, ask yourself if the line specification logic is necessary (it isn't all that clear to me what this check is for). Use nargin to determine if you have the correct number of inputs, and isfield to ensure that both inputs have x and y fields.

[Iris]

Do i define the point structure in another file?

[Iris]

I have taken your suggestion and changed my code. I see your point that the line check isn't necessary. Can you take a look at this rewritten one if there are any logic corrections or improvements that I should make?

function [ out ] = pointDist3( pointpair1, pointpair2)
%FUNCTION pointDist3 takes in any two pairs of points and 
% Calling sequence:
%   out = pointDist3(varargin)
%DEFINE VARIABLES
% minargs, maxargs = error checking variables 
% pointpair1 = structure containing fields for point 1: x1 and y1
% pointpair2 = structure containing fields for point 2: x2 and y2
% out = structure containing field distance
minargs = 4; 
maxargs=8;
nargchkin(minargs,maxargs);
%CHECK FOR VALID INPUT
if ~isfield(pointpair1,'x', pointpair2, 'x' ) || ~isfield(pointpair1,'y', pointpair2, 'y')
    error('Input argument does not contain fields "x" and "y" for both points');
else

      out = sqrt((pointpair1.x-pointpair2.x)^2+(pointpair1.y-pointpair2.y)^2);

end

[Geoff Hayes]

When I run the above code, I observe the error

 Error using isfield
 Too many input arguments.

because the code is trying to pass too many inputs to isfield. You can only check one field per structure at a time. So your above condition would become

 if ~isfield(pointpair1,'x') || ~isfield(pointpair1,'y') || ...
    ~isfield(pointpair2,'x') || ~isfield(pointpair2,'y')

You also need to add a check to make sure that both input parameters are being passed into the function. Use exist to check for their existence. This could replace the nargchkin call which doesn't seem appropriate for this function.

[Iris]

thanks!

Answer 2

[Meet Vora]

clc;
clear all;
close all;

point = struct('x',[],'y',[]);

point(1).x = 5;
point(1).y = 3;

point(2).x = 4;
point(2).y = 2;

display(dist3(point));

    1.4142

function distance = dist3(point)
        
        distance = sqrt((point(1).x - point(2).x)^2 + (point(1).y - point(2).y)^2);

end

[Deven Kyser]

The real GOAT