我有一个对象数组：
const bookDetails = [{"author":"john","readingTime":12123},
{"author":"romero","readingTime":908},
{"author":"romero","readingTime":1212},
{"author":"romero","readingTime":50},
{"author":"buck","readingTime":1902},
{"author":"buck","readingTime":12125},
{"author":"romero","readingTime":500},
{"author":"john","readingTime":10},
{"author":"romero","readingTime":230},
{"author":"romero","readingTime":189},
{"author":"legend","readingTime":12}
{"author":"john","readingTime":1890}]
我尝试计算每个作者的中位数。这是我计算给定数组中位数的函数：
//To calculate the median for a given array
function medianof2Arr(arr1) {
var concat = arr1;
concat = concat.sort(function (a, b) { return a - b });
var length = concat.length;
if (length % 2 == 1) {
// If length is odd
return concat[(length / 2) - .5]
} else {
return (concat[length / 2] + concat[(length / 2) - 1]) / 2;
}
}
但我想分别计算每个作者的中位数。我怎样才能做到这一点？
{"john": 1890, "romero": 365, "buck": 7014, "legend": 12}
您可以首先按作者对您的输入进行分组，以获得此数据结构：
{
"john": [12123, 10, 1890],
"romero": [908, 1212, 50, 500, 230, 189],
"buck": [1902, 12125],
"legend": [12]
}
然后你可以在所有这些数组上调用中值函数，并用你从调用中得到的值替换这些数组：
function median(arr) {
arr = [...arr].sort((a, b) => a - b);
let mid = arr.length >> 1;
return arr.length % 2 ? arr[mid] : (arr[mid-1] + arr[mid]) / 2;
}
const bookDetails = [{"author":"john","readingTime":12123}, {"author":"romero","readingTime":908}, {"author":"romero","readingTime":1212}, {"author":"romero","readingTime":50}, {"author":"buck","readingTime":1902}, {"author":"buck","readingTime":12125}, {"author":"romero","readingTime":500},{"author":"john","readingTime":10},{"author":"romero","readingTime":230}, {"author":"romero","readingTime":189}, {"author":"legend","readingTime":12},{"author":"john","readingTime":1890}];
// Create a key for each author, and link them with an empty array
let result = Object.fromEntries(bookDetails.map(({author}) => [author, []]));
// Populate those arrays with the relevant reading times
for (let {author, readingTime} of bookDetails) result[author].push(readingTime);
// Replace those arrays with their medians:
for (let author in result) result[author] = median(result[author]);
console.log(result);请注意，降压的中位数不是您预期输出中的整数 7014，而是 7013.5
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