Jacek Wesołowski@sos I think I'd try to feed the sine into a sigmoid function. Sigmoids can be parametrized, so you can control the steepness of the slope and the range of values (it doesn't have to be -1 to 1).
GNU social JP is a social network, courtesy of GNU social JP管理人. It runs on GNU social, version 2.0.2-dev, available under the GNU Affero General Public License.
All GNU social JP content and data are available under the Creative Commons Attribution 3.0 license.