Hi,
for your first question you can use :
p = polyfit(A(:,3),A(:,2),1);
Pay attention to use one like degree .
For the second question the following code should work , but i dont know if there is a way to dont use for loop:
b = unique(A(:,1));
degree=1;
p=zeros(size(b,1),degree+1);
for i=1:size(b,1)
ind = find(A(:,1)==b(i));
p(i,:) = polyfit(A(ind,3),A(ind,2),1);
end
