idl programming language - IDL for loop overwrites data -

i have problem for-loops in idl.

for sl=0,2 begin  ; number of hours  t=90,90 begin   ; timesteps each hour   rad_num = 0, 3 begin   ; number of radars    ibin = 0, 333 begin   ; distance radar      iray = 0, 359 begin   ; angle         if finite(input(ibin,iray,rad_num)) eq 1 begin         bin = bin_index(ibin,iray,rad_num)         ray = ray_index(ibin,iray,rad_num)  ; necessary because of different grids           array(sl,t,ray,bin)=array(sl,t,ray,bin)+ input(ibin,iray,rad_num)         array_n(sl,t,ray,bin) = array_n(sl,t,ray,bin) + 1.         endif       endfor      endfor     endfor    endfor   endfor  array = array / array_n 

when stopped program after first sl-loop-step, following:

 print, array[0,90,315,49]      44.0.673 

but when don't stop program, this:

 print, array[0,90,315,49]     -nan 

it seems, program overwrites data of previous loop-step. when make scatter-plot, have points of last loop-step only...

do see mistake? lot! kiki

you don't assign dwd in code show (and code won't compile as-is because of enddo's -- assume had rewrite code instead of copy-and-past reason?).