Dartで使いそうなListの統計処理集

8980 ワード
Flutter Dart Dart テキストリンク

1.合計

void main() {
  final list = [1, 2, 3, 4, 5];
  final sum = list.reduce((a, b) => a + b);
  print(sum); // 15
}

2.最大値、最小値

import 'dart:math';

void main() {
  print([1,2,8,6].reduce(max)); // 8
  print([1,2,8,6].reduce(min)); // 1
}

3.平均

void main() {
  final list = [1, 2, 3, 4, 5];
  final mean = list.reduce((a, b) => a + b) / list.length;
  print(mean) // 3;
}

4.中央値

void main() {
  list.sort();
  final list = [1, 2, 3, 4, 5];
  final length = list.length;
  int median;

  if (length % 2 == 1) {
    median = list[(length/2 + 0.5).toInt()];
  } else {
    median = ((list[length~/2] + list[length~/2 + 1]) ~/ 2);
  }

  print(median) // 3;
}

5.標準偏差

import 'dart:math';

void main() {
  final list = [1, 2, 3, 4, 5];
  final mean = list.reduce((a, b) => a + b) / list.length;
  final standardDeviation = sqrt(
    final squaredDifference = list.map((current) {
      var difference = current - mean;
      return pow(difference, 2);
    }).reduce((previous, current) =>
      previous + current
    ) / list.length;
  );

  print(standardDeviation); // 1.58113883008
}
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