Separating positive and negative numbers?

Hi, say I have a column of data. Each entry is either a positive or negative number. I would like to be able to sort out the positive numbers from the negative numbers so that I can find the sum of just the positive numbers and just the negative numbers (the columns are 1000s of entries so handpicking would be very time-exhausting). Is there a way to do this? Any help would be greatly appreciated.

use SUMIF

e.g. for negative numbers

=SUMIF(F1:F10000,"<0")

and for positive

=SUMIF(F1:F10000,">0")

Ed