Why doesn't this return the correct value?

Dear all

I currently have an array called good_index.  Some of the elements are
>=3D0 and others are <0.  I want to write a code that firstly finds how
many of these elements are greater than zero and use this number to
produce another array (called good_indexed_precip) with that number of
elements.  Then I want it to search through each element of good_index
in turn.  If upon searching it finds that the element is >=3D0 I want it
to find the value of that element in good_index.  I then want to find
the data stored in the index given by that value in another array
called precip_change.  The code I've written is below:

=3D=3D=3D=3D=3D
counter_2 =3D 0
number =3D total(good_index ge 0, /int) ;this counts how many elements
in good_index are >=3D zero
print, number     ;this gives the correct answer 6

	FOR s=3D0, (N_ELEMENTS(good_index)-1) DO BEGIN
		good_indexed_precip=3Dfltarr(number)
		IF good_index[s] ge 0 THEN BEGIN
				good_indexed_precip[counter_2] =3D precip_change[good_index[s]]
				counter_2++
		ENDIF
	ENDFOR
=3D=3D=3D=3D=3D

Unfortunately, it then prints good_indexed_precip with all 6 elements
zero, even though the values of precip_change[good_index[s]] are non-
zero.

If I were to put in the data by hand, eg say
good_indexed_precip[0] =3D precip_change[good_index[0]]
good_indexed_precip[1] =3D precip_change[good_index[13]]
This works fine, so I can't see why my loop isn't working correctly.
I know that the 0th &1st element of good_index are both >=3Dzero, yet if
I run the loop: FOR s=3D0, 1 DO BEGIN etc and print good_indexed_precip
it only has a non-zero value in the 1st element and not the 0th
element!

Thanks for all your help in advance.
Chlo=E9