How to plot a weighted line through an origin point

Hi all, so i am trying to plot lines as shown in the image below but with them both going through an origin point at the top centre of the figure where the injection nozzle would be. The code below shows the scanning for first and last white pixels(the image below is a negative, to give a more realistic view) and then an attempted weighting process to fit the lines to the origin, however , this hasn't worked. I think the problem lies where no white pixels were found at the top and therefore these rows haven't been taken into consideration.My reasoning for this is that size(leftColumns) and size(X) is 260, whilst BW_Length is 299. So maybe the solution comes from somehow including these rows, which i unfortunately don't know how to do. But i may well be wrong. Does anyone have any ideas? Thank you!

BW_Length=size(BW, 1); 
      next_row=1;
      for row = 1:BW_Length
          row_index=find(BW(row, :)>0, 1,'first');
          if ~isempty(row_index)
              leftColumns(next_row)=row_index;
              rightColumns(next_row)=find(BW(row, :)>0, 1,'last');
              X(next_row)=row;
              next_row=next_row+1;
          end
    end  

w=1-(X/BW_Length);

    ab1=wpolyfit(X,leftColumns,1,w);
    ab2=wpolyfit(X,rightColumns,1,w);

Answer 1

[Image Analyst]

You don't want to include those rows. They don't have the plume in them so why should you include them?