How do I draw a gui line?

I know how to draw a line with a part, but not with a gui.

function line(x,y)
    local v1 = Vector2.new(x.X.Offset,x.X.Offset)
    local v2 = Vector2.new(y.Y.Offset,y.Y.Offset)
    local center = (v1+v2)/2
    local dis = (v1-v2).magnitude
    local g = Instance.new("Frame")
    g:ClearAllChildren() --ignore this
    g.Rotation = center.X
    g.Size = vector2(dis,1)
    g.Position = UDim2.new(0,center.X/2,0,center.Y)
    g.BorderSizePixel = 0
    g.BackgroundColor3 = Color3.new(1,0,0)
    g.Parent = f
    return g
end

This doesn't work right. Help would be appreciated .