crossfilter , dc.js Counting unique value in dimension

Question

I am trying to create a bar chart (cross filter and dc js) to show how many people (unique) participated in an event

[ {"Year: 2015" , "Name:Person1"}, {"Year: 2015" , "Name:Person2"}, {"Year: 2015" , "Name:Person3"}, {"Year: 2015" , "Name:Person1"}, {"Year: 2015" , "Name:Person1"}, {"Year: 2016" , "Name:Person4"}, {"Year: 2016" , "Name:Person4"}, {"Year: 2016" , "Name:Person1"}, ]

I am plotting Year on X axis and Count on Y axis. Right now with Reduce count on Year I get

Year: 2015 Count:3 -> person 1,2,3 Year: 2016 Count:2 -> person 1,4

Sample code

yeardimension.group().reduceCount(function(d) { return d.year })

I want to get unique value and expected value

Year: 2015 Count:5 Year: 2016 Count:3

How can I achieve this in cross filter and dc js?

It looks like your expected and received values are reversed in your question - the unique counts are 3 and 2, and reduceCount (which doesn't take a parameter btw) returns 5 and 3, no? — Gordon
– Gordon, Commented Apr 11, 2016 at 13:23

Community · Accepted Answer · 2017-05-23 12:16:06Z

1

You would need to build a custom reducer, which is quite complex. There is an example here that gets at the right idea, though it will not be very fast and will break for certain keys as not all JS strings are valid property names: Crossfilter reduce :: find number of uniques

You can use Reductio's exception aggregation functionality to build fast and robust versions of these reducers easily. Or you may want to keep an eye on Universe, which aims to make this easy in a different way, using Reductio and Crossfilter under the covers.

edited May 23, 2017 at 12:16

CommunityBot

11 silver badge

answered Apr 8, 2016 at 13:26

Ethan Jewett

6,01019 silver badges25 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Jan.V Over a year ago

thanks for your reply.I indeed tried adding custom java script but it did not work

Jan.V Over a year ago

thanks for your reply.I indeed tried adding custom java script but it did not work . Is it because my dimension is on Year and while trying to reduce it i am trying to get uniques for Name. My bar chart dimension and group are on year and count for year so even after putting the custom js logic, cross filter still tries to get count for all records for particular year

Ethan Jewett Over a year ago

Please share the complete code that replicates your problem. Even better would be to create a working example using JSfiddle or Codepen.

Ramesh Rajagopalan Over a year ago

The Exception aggregation works fine for me. Thanks for the answer.

Collectives™ on Stack Overflow

crossfilter , dc.js Counting unique value in dimension

1 Answer 1

4 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Linked

Related