Implementing a new class,

I have a task in my university to make a line made out of 3 points by modifying the 2-point-line I already have. could anyone help me?

the 2-point line is:

classdef MgGeoLine2Point < mgen.MgGeoLine
    % A 2-point line of the geometry

      properties (Access = private)
          geoPoints = mgen.MgGeoPoint.empty(0,2);
          gridNodes = mgen.MgGridNode.empty(0,0);

          numTargetGridNodes  = 0;

          switchGridNode = false;
          switchGeoPoint = false;

          normFunction = mgen.MgNormFunction();
      end
      %
      methods
          %%constructor
          function obj = MgGeoLine2Point(geoPoints, numNodes, normFunction)
              if nargin >= 2
                  obj.geoPoints = geoPoints;
                  obj.numTargetGridNodes = numNodes;
                  obj.normFunction = mgen.MgNormFunction( mgen.MgNormFunctionType.Linear );
              end
              if nargin >= 3
                  obj.normFunction = normFunction;
              end
          end
          %%print data
          function str = print(self)
              str = sprintf( 'MgGeoLine2Point: gn1.id = %2d, gn2.id = %2d\n', self.gridNodes(1).id, self.gridNodes(end).id );
              %
              for gn = self.gridNodes
                  str = [ str, gn.print(), '\n' ];
              end
          end
          %%---------------------------------------------------------------------
          function p = getGeoPoint(self,id)
              if self.switchGeoPoint
                  p = self.geoPoints(3-id);
              else
                  p = self.geoPoints(id);
              end
          end
          function g = getGridNode(self, id)
              if ~self.switchGridNode
                  g = self.gridNodes(id);
              else
                  g = self.gridNodes(end-id+1);
              end
          end
          function setNumTargetGridNodes(self, num)
              self.numTargetGridNodes = num;
          end
          function num = getNumTargetGridNodes(self)
              num = self.numTargetGridNodes;
          end
          function switchStartGridNode(self)
              self.switchGridNode = ~self.switchGridNode;
          end
          function switchStartGeoPoint(self)
              self.switchGeoPoint = ~self.switchGeoPoint;
          end
          function resetStartGridNode(self)
              self.switchGridNode = false;
          end
          function resetStartGeoPoint(self)
              self.switchGeoPoint = false;
          end
          %
          function g = getCommonGridNode(self, geoline)
              %
              if self.getGridNode(1).id ~= geoline.getGridNode(1).id
                  geoline.switchStartGridNode();
              end
              if self.getGridNode(1).id ~= geoline.getGridNode(1).id
                  self.switchStartGridNode();
              end
              if self.getGridNode(1).id ~= geoline.getGridNode(1).id
                  geoline.switchStartGridNode();
              end
              if self.getGridNode(1).id ~= geoline.getGridNode(1).id
                  disp('MgGeoLine2Point:getCommonGridNode() --> GridNodes not matching!')
              end
              g = self.getGridNode(1);
          end
          %
          function g = getCommonGeoPoint(self, geoline)
              if self.getGeoPoint(1) ~= geoline.getGeoPoint(1)
                  geoline.switchStartGeoPoint();
              end
              if self.getGeoPoint(1) ~= geoline.getGeoPoint(1)
                  self.switchStartGeoPoint();
              end
              if self.getGeoPoint(1) ~= geoline.getGeoPoint(1)
                  geoline.switchStartGeoPoint();
              end
              if self.getGeoPoint(1) ~= geoline.getGeoPoint(1)
                  disp('MgGeoLine2Point:getCommonGeoPoint() --> GeoPoints not matching!')
              end
              g = self.getGeoPoint(1);
          end
          %
          function alignLines(self, geoline)
              self.getCommonGeoPoint(geoline);
              self.switchStartGeoPoint();
              %
              if length(self.gridNodes) > 0
                  self.getCommonGridNode(geoline);
                  self.switchStartGridNode();
              end
          end
          %
          function gnv = makeGridNodes(self, gridnodes)
              %
              gnv = gridnodes;
              % 
              if length(self.gridNodes) > 0
                  return;
              end
              %
              run_id   = 1+length(gridnodes);
              dim      = self.numTargetGridNodes;
              segments = dim-1;
              x0       = self.geoPoints(1).coord(1);
              x1       = self.geoPoints(1).coord(2);
              lx0      = self.geoPoints(2).coord(1) - x0;
              lx1      = self.geoPoints(2).coord(2) - x1;
              %
              % occupy vector of GridNodes with the existing ones
              self.gridNodes = mgen.MgGridNode.empty(0,dim);
              self.gridNodes(1)   = self.geoPoints(1).gnode;
              self.gridNodes(dim) = self.geoPoints(2).gnode;
              %  
              % set function values
              self.normFunction.vals(1) = segments;
              if self.normFunction.vals(2) == 0
                  self.normFunction.vals(1) = segments;
              end
              if self.normFunction.vals(1) == 1
                  self.normFunction.vals(2) = segments;
              end
              %
              % generate new GridNodes
              for ii = 1:segments-1
                  scale = self.normFunction.eval( ii/segments );
                  self.gridNodes(ii+1) = mgen.MgGridNode( run_id, [x0+scale*lx0, x1+scale*lx1] );
                  gnv(end+1) = self.gridNodes(ii+1);
                  run_id = run_id + 1;
              end
          end
          function gp = getGeoPoints(self)
              gp = self.geoPoints;
          end
          function gn = getGridNodes(self)
              gn = self.gridNodes;
          end
      end
  end

Anybody could help me a little bit?

[Vineeth Kartha]

Hi,

Please provide a description of the exact help that you are looking for. Are you facing any errors or do you need help in doubts regarding the code. providing a detailed description will let the community provide you with better answers.

Regards Vineeth

[Damon Moazami]

I don't understand the code properly, the class above, gets 2 points of geometry and draws a straight line between them. My task is to write a code that draws a quadratic curve between three points "geoPoint". I already have a function that does that but I don't know how and where to implement it

function cfun(A,B,C,N)
M = [1 0 0 0 0 0; 0 1 0 0 0 0; 1 0 0.5 0 0.25 0; 0 1 0 0.5 0 0.25; 1 0 1 0 1 0; 0 1 0 1 0 1];
b = [A; B; C];
x = M\b;
a0 = x(1:2);
a1 = x(3:4);
a2 = x(5:6);
clf; hold on;
plot([A(1) B(1) C(1)], [A(2), B(2), C(2)], 'ro');
t = linspace(0,1,100);
x = a2 * t.^2 + a1 * t + a0 * ones(1,length(t));
plot(x(1,:), x(2,:), 'b-');
t = linspace(0,1,N);
x = a2 * t.^2 + a1 * t + a0 * ones(1,length(t));
plot(x(1,:), x(2,:), 'kx');
end

Answer 1

[Guillaume]

" the class above, gets 2 points of geometry and draws a straight line".

The class you've posted does no drawing whatsoever. And despite its name also does not appear to restrict itself to storing only two points. The constructor certainly does not appear to restrict the numbers of points stored. It looks like the only function that sort of assumes two points is the debugging function print (it prints only two points, the first and the last) but it also looks like getGeoPoint assumes 3 points.

In fact, it looks like the methods implemented in the class actually belong to the base class. Are they just a copy of the functions in MgGeoLine? To me it looks like somebody either didn't understand inheritance or completely misnamed their classes.

It's near impossible to answer your question in any case as we don't know anything about the base class from which MgGeoLine2Point derives. It certainly does not restrict itself to storing points, since there's also something about a norm function and something about creating a grid.

[Damon Moazami]

I have uploaded the whole framework if you want to take a look at it!

[Guillaume]

I've had a brief look. This looks like a work in progress that's not been tested properly. There are exactly 4 differences between MGeoLine2Point and MgeoLine3Point:

1. The private attribute of the properties has been commented out in MgeoLine3Point. This has no effect on behaviour.
2. The 'starting value' of the properties are slightly different. Theses values will never be used anyway since they get replaced in the constructor, so no effect.
3. The check for the number of inputs has been increased by one in MgeoLine3Point. This is indication that whoever wrote the code don't really know what they're doing. The number of declared inputs hasn't changed so the check does not work anymore. A bug.
4. the print method prints a different class name. No change otherwise.

That's it. There's no functional difference between the two classes. Apart from the bug in MgeoLine3Point, you can use one instead of the other with no difference in behaviour.

Therefore, I would recommend you go back to whoever wrote this code and ask for clarification and to provide documentation on how to use the classes.

[Damon Moazami]

I'll do that, Thank you very much.