delete points of a serie

[ferri_marllo gva es]

Hi!!
i'm making an apllication using gtk and I need to delete negative points of a
serie.


for example...i have a file like this:


t px py

1 20 15
2 -6 30
3 4  3

I've declared static gdouble t[NPOINTS],px[NPOINTS],py[NPOINTS]because then i'll
plot using gtkplot.

at first i read the first line an identify t,px,py...then i continue until the
end of the file identifying t[i],px[i],py[i],i=1-NPOINTS
so i build serie t,serie px,and serie py.
during the reading...i would like that if any numeber is negative, delete it and
not appear in the corresponding serie.
So...at the end i want to obtain:
(in this case)

serie t 1,2,3
serie px 20,4
serie py 15,30,3

how can i do it??
can you help me?? thanks a lot