yAxis label value does not match the each bar value
eg : const barData = [ [0, 1], [1, 3], [3, 7], [4, 9], ]; but the '4' bar match the yAxis value is 7 in chart...
Can you post a screenshot? Just for clarity as I'm combing through these. Thank you!
Hi. I believe i can provide more info. I have the same thing:

with same data as example: chartData: [ [0, 1], [1, 3], [3, 7], [4, 9], ], (Completely unrelated to rest of page)
and chart: <Chart style={styles.chart} data={this.state.chartData} verticalGridStep={5} type="line" showDataPoint={true} tightBounds={true} />
style:
chart: { width: 300, height: 150, },
And i think it is related with vertical grid step. Because when i set its value to be equal to the number of points, this happens:

This should be fixed with the react-native-svg change. You can try out that branch for a preview in the meantime.
As a generic FYI — I am no longer able to maintain this library. I recommend checking out victory-native as it's much more maintained.