Dear R-list Members, Sorry if I have double posted this message. I am not sure if my previous message got through. Can someone explain me what exactly is the vertical bar of the cross in the upper right corner of the spectrum plot produced by spec.plot? I know it is the 95% confidence of the spectrum, but do not understand what it is exactly. Based on the section 9.5 of Bloomfield 2000, I understand how the pointwise 95% CI of spectrum at a certain frequency is computed. Is the vertical bar of the cross for the mean spectrum or total spectrum? What is the exact interpretation of the vertical bar? Many thanks in advance! Sincerely, Guiming Wang