pro pp_plot_with_ttest,a,b,z=z,mask=mask,sig=sig,_extra=e

; Purpose: plot diff of avg of 2 vectors of pp-fields, and add in their sig
; Category: pp statistics
; Inputs:
;	a,b - vectors of pp-fields
; Keywords:
;	z=z - if supplied, use the z-field given. Saves time. If supplied undefined,
;	      returns the value calculated
;	mask=mask - returns the mask field created for significance
;	sig=sig - change the default of 95% (0.05)

@comm_error

a1=pp_avg(a)
b1=pp_avg(b)
if (n_elements(sig) eq 0) then sig=0.05

pp_plot,la=90,ster=0,pp_diff(a1,b1),_extra=e

if (n_elements(z) eq 0) then z=pp_ttest(a,b)
mask=pp_set_mask(z,'f1.data lt '+shtstr(sig))
mask_plot,fil=-!p.color,mask,ori=45,/li,th=2

print,'Mask covers: ',pp_mask_fraction(mask)*100,' % of area'

end