BezierCurve do not always work

[MattiaConfalonieri]

Hi, maybe i have found an issue (i am not sure)

BezierCurve, not work always.

My impression is that if the array of value contain two equal data in sequence that invalidate the bezier.

Issue reply:

arrayOfValues = [[NSMutableArray alloc] initWithObjects: [NSNumber numberWithFloat:57.0],[NSNumber numberWithFloat:57.0],[NSNumber numberWithFloat:0],[NSNumber numberWithFloat:57.6],[NSNumber numberWithFloat:0],[NSNumber numberWithFloat:0],[NSNumber numberWithFloat:58.0],[NSNumber numberWithFloat:0],[NSNumber numberWithFloat:0],[NSNumber numberWithFloat:0],[NSNumber numberWithFloat:58.0], nil];

arrayOfValues = [[NSMutableArray alloc] initWithObjects: [NSNumber numberWithFloat:58.0],[NSNumber numberWithFloat:57.0],[NSNumber numberWithFloat:0],[NSNumber numberWithFloat:57.6],[NSNumber numberWithFloat:0],[NSNumber numberWithFloat:0],[NSNumber numberWithFloat:58.0],[NSNumber numberWithFloat:0],[NSNumber numberWithFloat:5],[NSNumber numberWithFloat:0],[NSNumber numberWithFloat:58.0], nil];

NOTE: in the second example you can see another little issue, where there are the two 0 value in sequence the bezier curve drop down under the 0 value.

I hope this help, let me know if you need other test, to resolve the issue because the library is AMAZING!!!!

[Boris-Em]

Hi @MattiaConfalonieri,
Thank you for your very thorough contribution!
This bug had been spotted in the issue #63, but due to the lack of information on how to repro the issue, I had to close it.
I have a pretty good idea of where this could come from. I'll take a look at it tonight.

Regarding the drops under 0, this is unfortunately (I believe) inevitable and due to the bezier curves.

[Boris-Em]

@MattiaConfalonieri,
For some reason I can't repro this bug. Even when I use your array. I will try to investigate more when I find some time this week end.

[MattiaConfalonieri]

Don't worry, your work is great.

[danhje]

I have the exact same issue. It shouldn't be hard to repro, it happens a lot. And MattiaConfalonieri is correct, it happens when if there are two equal data in sequence. The BezierCurve will work up to that point, but not after (se the last picture below, where the BezierCurve is working great until the two identical data points.

A very dirty workaround is to add a tiny random number to all values, like so:

• (CGFloat)lineGraph:(BEMSimpleLineGraphView *)graph valueForPointAtIndex:(NSInteger)index {
  double r = drand48() / 1000.0;
  return [[self.data objectAtIndex:index] floatValue] + r;
  }

Bezier is not working:

Bezier is working:

Bezier is partially working:

[cuva]

By binding the height of the graph to a pan gesture it's possible to detect that for every two pt / pixel the bezier curve breaks, while it works for the next, doesn't for the one after etc...

Not sure if that would help debugging.

[Boris-Em]

Thank you so much everyone for your help with this bug.
I just pushed a commit (47a583d) that should fix the issue. If I could get a confirmation that it is now fixed it would be perfect!

[MattiaConfalonieri]

WOW!
for me the issue is solved! (tested on iOS7 and iOS8)

[cuva]

Beautiful - nice work, I love the lib. Thanks mate!

[cuva]

It seems to be working better, but here I found a dataset for which it doesn't:

[97.0, 99.0, 93.0, 98.0, 90.0, 92.0, 94.0, 98.0, 93.0, 99.0]

with maxValueForLineGraph = max(set)
and minValueForLineGraph = min(set)

Cheers

[skywinder]

@Boris-Em following by your commit above (12587c0) - it seems that this issue should be closed?