dmhall0 Posted February 20, 2012 Share Posted February 20, 2012 I have elevation points in an array. I need to calculate the difference between each point to get the total gain, total loss, and net. Example: point 2 - point 1 = +100 point 3 - point 2 = -10 point 4 - point 3 = -20 ... and so on So my outputs need to be: Total Gain = +100 Total Loss = -30 Total Net = +70 Any help would be great. I am still new to coding but this seems complicated. Link to comment https://forums.phpfreaks.com/topic/257418-calculating-difference-between-points-in-array/ Share on other sites More sharing options...
Pikachu2000 Posted February 20, 2012 Share Posted February 20, 2012 Where are the values coming from? Link to comment https://forums.phpfreaks.com/topic/257418-calculating-difference-between-points-in-array/#findComment-1319377 Share on other sites More sharing options...
dmhall0 Posted February 20, 2012 Author Share Posted February 20, 2012 MySQL table that I pulled out with a query. Link to comment https://forums.phpfreaks.com/topic/257418-calculating-difference-between-points-in-array/#findComment-1319378 Share on other sites More sharing options...
requinix Posted February 21, 2012 Share Posted February 21, 2012 Which looks like...? Link to comment https://forums.phpfreaks.com/topic/257418-calculating-difference-between-points-in-array/#findComment-1319379 Share on other sites More sharing options...
Pikachu2000 Posted February 21, 2012 Share Posted February 21, 2012 That's what I was kind of thinking. You could do the math in the query as well. SELECT point 2 - point 1 AS diff2_1, point 3 - point 2 AS diff3_2, point 4 - point 3 AS diff4_3 FROM table WHERE whatever . . . Then the calculated values would be in the array produced by whichever mysql_fetch_* function you use. Link to comment https://forums.phpfreaks.com/topic/257418-calculating-difference-between-points-in-array/#findComment-1319380 Share on other sites More sharing options...
dmhall0 Posted February 21, 2012 Author Share Posted February 21, 2012 SELECT elevation FROM track_points WHERE activity_id = '813'; There could be thousands of points (rows) for the one activity, so doing the work in the query is pretty much out of the question. Link to comment https://forums.phpfreaks.com/topic/257418-calculating-difference-between-points-in-array/#findComment-1319381 Share on other sites More sharing options...
Pikachu2000 Posted February 21, 2012 Share Posted February 21, 2012 Then you're going to need to elaborate a little more, I believe. Are you trying to go through the array programatically, and just find the difference of a point and the previous point, regardless of the number of points in the array? Link to comment https://forums.phpfreaks.com/topic/257418-calculating-difference-between-points-in-array/#findComment-1319382 Share on other sites More sharing options...
dmhall0 Posted February 21, 2012 Author Share Posted February 21, 2012 I am wanting to find the difference between every 2 points, just like in my first post example, then sum all the numbers > 0, sum all the numbers < 0, then give me the total. So if there are 1000 points in the array, I would get 500 numbers. Link to comment https://forums.phpfreaks.com/topic/257418-calculating-difference-between-points-in-array/#findComment-1319383 Share on other sites More sharing options...
dmhall0 Posted February 21, 2012 Author Share Posted February 21, 2012 Found a way to solve it via MySQL here. http://www.freeopenbook.com/mysqlcookbook/mysqlckbk-CHP-12-SECT-13.html Thanks for the help though. Link to comment https://forums.phpfreaks.com/topic/257418-calculating-difference-between-points-in-array/#findComment-1319403 Share on other sites More sharing options...
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