How to find the parabola using RANSAC method in Matlab

Can anyone here suggest with ideas for finding the parabola using RANSAC where,

function [bestParameter1,bestParameter2] = ransac(data,num,iter,threshDist,inlierRatio

   figure;plot(data(1,:),data(2,:),'o');hold on;
   number = size(data,2); % Total number of points
   bestInNum = 0; % Best fitting line with largest number of inliers
   bestParameter1=0;bestParameter2=0; % parameters for best fitting line
   for i=1:iter
   %%Randomly select 2 points
       idx = randperm(number,num); sample = data(:,idx);   
   %%Compute the distances between all points with the fitting line 
   kLine = sample(:,2)-sample(:,1);% two points relative distance
       kLineNorm = kLine/norm(kLine);
       normVector = [kLineNorm(2),-kLineNorm(1)];%Ax+By+C=0 A=-kLineNorm(2),B=kLineNorm(1)
       distance = ((normVector)*(data - repmat(sample(:,1),1,number)));                      
    
    %%Compute the inliers with distances smaller than the threshold
       inlierIdx = find(abs(distance)<=threshDist);
       inlierNum = length(inlierIdx);
   %%Update the number of inliers and fitting model if better model is found     
       if inlierNum>=round(inlierRatio*number) && inlierNum>bestInNum
           bestInNum = inlierNum;
           parameter1 = (sample(2,2)-sample(2,1))/(sample(1,2)-sample(1,1));
           parameter2 = sample(2,1)-parameter1*sample(1,1);
           bestParameter1=parameter1; bestParameter2=parameter2;
       end
   end

   %%Plot the best fitting line
   xAxis = -number/2:number/2; 
   yAxis = bestParameter1*xAxis + bestParameter2;
   plot(xAxis,yAxis,'r-','LineWidth',2);

end

#Source from Wiki, In the above code the random points to be choosen is 3 instead 2 in my case(as i have to get Parabola and not the line) but the calculation of distance seems to be a problem. Can anyone help me with this?

Thank you so much for understanding in advance