Thank you very much. I am new to this mailing list, so i missed it. Jakub Ladman
Dne sobota 10 březen 2007 00:48 Clark Christensen napsal(a): > A poster here, "Mikey C", wrote some math functions and posted them a month > or so ago. You might have a look at > http://www.mail-archive.com/[email protected]/msg21791.html > > -Clark > > ----- Original Message ---- > From: Jakub Ladman <[EMAIL PROTECTED]> > To: [email protected] > Sent: Friday, March 9, 2007 3:00:22 PM > Subject: Re: [sqlite] sin and similar functions > > Thank you very much. > Not only my english is poor, but my coordinated geometry too :-( > But my software will make much more geometrical computations, so probably > some in queries too. > Please let You (or someone) direct me to the relevant part of documentation > for defining new functions. > > Thank You > Jakub > > Dne pátek 09 březen 2007 23:35 Dennis Cote napsal(a): > > Jakub Ladman wrote: > > > I will have table with sequence of coordinates (two dimensional space) > > > and corresponding radiuses, so sequence of circles. And i need to use a > > > sqlite query to detect if a actual coordinates (after their > > > measurement) match some of the circle's square or not. And which > > > circle, if match. And this must be for low CPU consumption optimised, > > > so i am not sure, if separate sin table queries will be enough as fast > > > as i need at needed precission. > > > > > > The whole algorithm is proven on mssql by my colegue, but he is using > > > the native math functions. > > > > Jakub, > > > > I may not understand your problem completely, but it seems to me you can > > solve your problem without using any trigonometric functions. > > > > If you have a table of circles like this > > > > create table circle ( > > id integer primary key, > > cx real, > > cy real, > > r real > > ); > > > > You can find all the circles that contain a given point (px,py) using a > > simple query based in the distance between the point and the center of > > the circle. > > > > select id from circle > > where (px-cx)*(px-cx)+(py-cy)*(py-cy) < r*r; > > > > If you want to create a user defined distance function you could > > possibly speed up the calculation somewhat. You could then use a query > > like: > > > > select id from circle > > where distance(cx, cy, px, py) < r; > > > > where > > > > distance(cx, cy, px, py) = sqrt((px-cx)^2 + (py-cy)^2) > > > > HTH > > Dennis Cote > > > > > > ------------------------------------------------------------------------- > >-- -- To unsubscribe, send email to [EMAIL PROTECTED] > > ------------------------------------------------------------------------- > >-- -- > > --------------------------------------------------------------------------- >-- To unsubscribe, send email to [EMAIL PROTECTED] > --------------------------------------------------------------------------- >-- > > > > > > --------------------------------------------------------------------------- >-- To unsubscribe, send email to [EMAIL PROTECTED] > --------------------------------------------------------------------------- >-- ----------------------------------------------------------------------------- To unsubscribe, send email to [EMAIL PROTECTED] -----------------------------------------------------------------------------
