how to change LineChartDataSet without strange redraw issues?

[dcsim0n]

My code is used to fetch data from a radio scanner about noise levels, the data comes in 8bit integers over a tcp stream in small bits as the scanner moves across the radio spectrum.
I start with a DataSet of all zeros so that the proper frequency range is displayed from the start.

The first scan loop works as expected, but when the scanning loop repeats I begin to see strange results.

The function that is responsible for parsing and inserting data into the graph.
BlockGraph is a custom class which contains information about frequency boundaries and a ChartDataEntry set

func parseAndAppend(graphToUpdate graph: BlockGraph ,rawData: ScanPacket){
print("adding Data at (rawData.offset)")
let lowerBlockBound = graph.block.bounds.0 - 10
let offset = Int(rawData.offset)
for i in 0..<rawData.bytes.count{
let freq = lowerBlockBound + (offset + i)
let byteToGraph = rawData.bytes[i]
let dataPoint = ChartDataEntry(x: Double(freq), y: Double(byteToGraph))
if offset > graph.graphData.count{
graph.graphData.append(dataPoint)
}else{
graph.graphData.insert(dataPoint, at: (offset+i))
}
}

Charts Environment

**Charts version/Branch/Commit Number: 3.1.0
**Xcode version: 9.2
**Swift version: 4.0
**Platform(s) running Charts: ios11
**macOS version running Xcode: 10.13

[liuxuan30]

please ask on stack overflow. It seems your issue while scanning. Please also search old issues about dynamic update especially those tagged with GoodExample