Highstock custom min max approximation works properly only at some ranges -

i feeding highstock chart datas mysql. there variables stored every minute if want @ data past 3 months grouped. highstock's default approximation functions give low,high,averare,sum values only. min , max values important me made own approximation function is:

         approximation: function (arr) {                  // first time or point precalculated                           if ( !ginfo || ginfo.nextpoint) {                     // first time return first value (arr[0])                     var point = ginfo ? ginfo.nextpoint : arr[0];                     // save current data next iteration                         ginfo = {prev : arr, nextpoint : null};                     return point;                 } else {                     var prev = ginfo.prev,                         // concat current group previous 1                         data = prev.concat(arr),                         // min, max , positions                                 min = math.min.apply(null, data),                         max = math.max.apply(null, data),                         minidx = data.indexof(min),                         maxidx = data.indexof(max),                         // order min , max                         aprox = minidx < maxidx ? [min, max] : [max, min];                     // save next aproximation , return current                     ginfo.nextpoint = aprox[1];                     return aprox[0];                 }         }, 

actually didn't make found here in forum.

the problem gives me right results @ ranges shown in pictures below:

first picture @ max range - not ok: max range - can't see every min value

as changing range smaller can see every min value: this how should looke @ max range

it happening when zoom in datas grouped in 2 min intervals , scrolling left or right.

at first thought has way groups made changing grouppixelwidth: value did not help.

having min or max important me , can solve in highstock.

there seems error in approximation function. in 3rd line:

if ( !ginfo || ginfo.nextpoint) { 

if should evaluate false if !ginfo false (it after first time) , ginfo.nextpoint returns false, return false not if null (as set in function), when zero. changing if condition to:

if (!ginfo || ginfo.nextpoint !== null) { 

example error (before fix): http://jsfiddle.net/p2qvx24a/1/

example fix: http://jsfiddle.net/p2qvx24a/