Re: Graphing project

Are you generating simple bar graphs or something more complex like lines, best fit, scatter diagrams, etc? If it's just bar or column charts, maybe this will help a little. The algorithm I use to scale the axes uses logarithms to calculate the order of magnitude of the maximum value. In PHP, for example, if the maximum value is $themax and let's say $themax=400 for this example then you would do: $z = floor(log10($themax)) + 1; /* get the integer portion (characteristic) of the logarithm, plus 1 */ /* $z is now = 3 */ $z = pow(10,$z); /* raise it to the power 10 */ /* $z is now = 1000 */ while ($z/2 > $themax) { $z = $z/2; } /* chop $z in half a few times until it's less than your maximum. */ /* $z will now be = 500 for this example. This will be the */ /* maximum value of your axis. */ Then you just have to size your bars or columns as a percentage of the maximum. I use this to chart page hits and banner clicks per thousand impressions (a decimal value) and it works great. Jeff Markus wrote: > > Hi, > > I'd need some hints on how to program a coordinate system. I've been > searching for tutorials all over the web but haven't managed to find any > (surprising, isn't it?) > > I'm not asking you to write the whole stuff, but to give me something useful > to get going. What I'm about to build allows the user to input minimum and > maximum values for x & y shown on the graph and also scale values etc. As I > have only little experience on graphics programming, this seems quite > difficult. > > Also if you know any tutorials on web (doesn't really matter what language, > Java, C/C++, Visual Basic goes fine too - as long as I get the idea). > > Thanks in advance, > Markus > > -- > PHP General Mailing List (http://www.php.net/) > To unsubscribe, e-mail: php-general-unsubscribe@lists.php.net > For additional commands, e-mail: php-general-help@lists.php.net > To contact the list administrators, e-mail: php-list-admin@lists.php.net