如何使用Crossfilter对Col2值为0的Col1列数据求和？

First off, the issue with your current code is that when d.col2 isn't 0, your callback function doesn't return anything (it implicitly returns undefined). Crossfilter's reduceSum expects a numeric value every time—returning undefined breaks the summation logic entirely.

Here's the fixed version of your code:

var stemTotal = this.ndx.groupAll().reduceSum(function(d) {
  // Return Col1 value if Col2 is 0, otherwise return 0 to exclude it from the sum
  return d.Col2 === 0 ? +d.Col1 : 0;
});

Key Things to Check: #

• Case Sensitivity: Make sure the property names (Col1 and Col2) match exactly with the keys in your data objects. Your original code used lowercase col1/col2, but your table shows uppercase initials—this mismatch would also cause your code to fail even if the logic was correct.
• Explicit Return: By returning 0 when the condition isn't met, we ensure the reducer always receives a valid number, so the sum calculates as expected.

To retrieve the final summed value, call:

console.log(stemTotal.value()); // Outputs the total sum of Col1 where Col2 equals 0

内容的提问来源于stack exchange，提问作者BillSut