javascript - dc.js - how to get the average of a column in data set - Stack Overflow

I have this below data.

col1    col2    value
a   01/01/14    10
a   01/01/14    35
a   01/01/14    68
a   01/01/14    21
a   01/01/14    24
b   01/01/14    26
b   01/01/14    35
b   01/01/14    39
b   01/01/14    87
c   01/01/14    25
c   01/01/14    63
c   01/01/14    11
c   01/01/14    25
c   01/01/14    35

If I wanted to take the sum of col1. I could do it by using col1Dim.group().reduceSum(function(d) { return d.value }). If I need the count i can replace sum with count.

But I'm here loooking for average. So to that. I need to take sum of col1 and count of col1.

Any idea how can i divide and get the average?

Please help. Stuck in this for almost 3 days.

I have this below data.

col1    col2    value
a   01/01/14    10
a   01/01/14    35
a   01/01/14    68
a   01/01/14    21
a   01/01/14    24
b   01/01/14    26
b   01/01/14    35
b   01/01/14    39
b   01/01/14    87
c   01/01/14    25
c   01/01/14    63
c   01/01/14    11
c   01/01/14    25
c   01/01/14    35

If I wanted to take the sum of col1. I could do it by using col1Dim.group().reduceSum(function(d) { return d.value }). If I need the count i can replace sum with count.

But I'm here loooking for average. So to that. I need to take sum of col1 and count of col1.

Any idea how can i divide and get the average?

Please help. Stuck in this for almost 3 days.

• javascript
• d3.js
• dc.js
• crossfilter

Share Improve this question Follow edited Nov 9, 2015 at 16:29 davidshinn 1,94611 gold badge1616 silver badges1717 bronze badges asked Feb 3, 2014 at 4:47 user3206082user3206082 4311010 silver badges1818 bronze badges 2

• How about getting the sum and the count and then the average is sum/count? – Tibos Commented Feb 3, 2014 at 4:51
• How can I do it with dc.js? – user3206082 Commented Feb 3, 2014 at 5:50

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1 Answer 1

Sorted by: Reset to default 16

You need to use the group.reduce(add, remove, initial) method, like:

var col1DimTotal = col1Dim.group().reduce(reduceAdd, reduceRemove, reduceInitial);

function reduceAdd(p, v) {
  ++p.count;
  p.total += v.value;
  return p;
}

function reduceRemove(p, v) {
  --p.count;
  p.total -= v.value;
  return p;
}

function reduceInitial() {
  return {count: 0, total: 0};
}

Because you're using dc.js, you'll need to use chart.valueAccessor method to use the average in your charts, like:

chart.valueAccessor(function(p) { return p.value.count > 0 ? p.value.total / p.value.count : 0; });