Ps_plot('v-dao','a_gacos',1,0,0,'ts') error

Hello everyone. When I execute ps_plot (‘v dao ‘,’ a_gacos’, 1,0,0, ‘ts’), the program reports an error
Interferogram (1) does not have a reference area
Subscription indices must either be real positive integers or logicals
Error in ps_plot (line 1963)
Maxph=phsort (round (length (phsort) *. 999));

Has anyone encountered a similar problem before? How should I solve it. Thank you everyone