function phi = limiter(a,l)
    if strcmp(l, 'minmod')
        b=ones(size(a));
        phi = minmod(b,a);
    elseif strcmp(l, 'MC')
        phi = MC(a);
    elseif strcmp(l, 'superbee')
        phi = superbee(a);
    elseif strcmp(l, 'van_leer')
        phi = van_leer(a);
    elseif strcmp(l, '')
        phi = ones(size(a));
    end
end