@tidyjs/tidy/dist/lib/vector/lag.js

Tidy up your data with JavaScript, inspired by dplyr and the tidyverse

'use strict';

Object.defineProperty(exports, '__esModule', { value: true });

function lag(key, options) {
  const keyFn = typeof key === "function" ? key : (d) => d[key];
  const {n = 1, default: defaultValue} = options != null ? options : {};
  return (items) => {
    return items.map((_, i) => {
      const lagItem = items[i - n];
      return lagItem == null ? defaultValue : keyFn(lagItem, i, items);
    });
  };
}

exports.lag = lag;
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