index.js

// BarGraph/index.js
import React  from 'react';
import { StyleSheet, Text, View, Dimensions } from 'react-native';

import Columns from './Columns';
import XAxis from './xAxis';
import YAxis from './yAxis';

export default function BarGraph({ data, color }) {
  let width = Dimensions.get('screen').width;
  let yAxisHeight = 325;
  let xAxisHeight = 30;
  let barsHeight = 315;

  return (
    <View style={styles.main}>
      <YAxis
        height={yAxisHeight}
        width={width} />

      <Columns
        data={data}
        width={width - 10}
        height={barsHeight}
        color={color} />

      <XAxis
        width={width - 10}
        height={xAxisHeight} />
    </View>
  );
}

const styles = StyleSheet.create({
  main: {
    marginVertical: 25,
    marginHorizontal: 0,
  }
});