# Doubt about forecast function usage **URL:** \ **Category:** GNU Radio\ **Created:** [May 27, 2013, 12:15pm UTC](https://www.ruby-forum.com/t/doubt-about-forecast-function-usage/235032 "2013-05-27T12:15:53Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [May 27, 2013, 12:15pm UTC](https://www.ruby-forum.com/t/doubt-about-forecast-function-usage/235032/1 "2013-05-27T12:15:53Z")
In which way should I use forecast function if the number of output items isn’t anyhow related to the number of input items. The relationship is more qualitative than quantitative. For example number of output elements depends on whether there is certain power inside the input strea, or similar. Best ---
**Author:** ![Nemanja\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/7bcc69/32.png) [@Nemanja\_S](https://www.ruby-forum.com/u/Nemanja_S)\ **Post date:** [May 27, 2013, 1:49pm UTC](https://www.ruby-forum.com/t/doubt-about-forecast-function-usage/235032/2 "2013-05-27T13:49:21Z")
On Mon, May 27, 2013 at 12:14:11PM +0200, Nemanja S. wrote: > In which way should I use forecast function if the number of output items isn’t > anyhow related to the number of input items. The relationship is more > qualitative than quantitative. For example number of output elements depends on > whether there is certain power inside the input strea, or similar. It doesn’t really matter, because you’re using a gr::block and therefore, you can always check both ninputitems and noutputitems. If you have a certain ratio when outputting, use that. At least, that will ensure enough space in the output buffer when you actually do have something going through the block. MB – Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Martin B. Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-43790 Fax: +49 721 608-46071 www.cel.kit.edu KIT – University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association ---
**Author:** ![Nemanja\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/7bcc69/32.png) [@Nemanja\_S](https://www.ruby-forum.com/u/Nemanja_S)\ **Post date:** [May 27, 2013, 4:08pm UTC](https://www.ruby-forum.com/t/doubt-about-forecast-function-usage/235032/3 "2013-05-27T16:08:27Z")
Thanks.