CODEWITHSUNDEEP
jsondc.jscrossfilter
NeilS
NeilS

Reputation: 85

Calculating totals in crossfilter.js using group().reduceCount and groupAll().reduceSum

I have a large JSON file with values similar to this example:

[
  {"date": "12/27/2012",  "temp": 23,  "pH": ".4"},
  {"date": "12/27/2012",  "temp": 23,  "pH": ".7"},
  {"date": "12/27/2012",  "temp": 23,  "pH": ".2"},
  {"date": "12/27/2012",  "temp": 23}
]

There will be instances where the pH value will not exist. I need to keep track on the page of how many instances of "temp" and "pH" there are. I don't have a problem doing this with a JavaScript loop, but I'd also like to see if I can do it with crossfilter.

Basically, is there something similar to groupAll().reduceCount().value(), that counts just the individual instances of the strings?

Here's a sample of the code inside the d3.json() block:

 var tempDim = xFilter.dimension(function(d) {return d.temp;}); 
 var tempGroup = tempDim.group().reduceCount(function(d) {return d.temp;});

 var tempCount = tempDim.groupAll().reduceCount().value();
 console.log("tempCount :"+tempCount); // 4

 var tempSum = tempDim.groupAll().reduceSum(function(d) {return d.temp;}).value();
 console.log("tempSum :"+tempSum); // 92

 //pH 
 var phDim = xFilter.dimension(function(d) {return d.pH;});
 var phGroup = phDim.group().reduceCount(function(d) {return d.pH;}); 

 var pHCount = phDim.groupAll().reduceCount().value();
 console.log("pHCount :"+pHCount); // Equal to 4, looking for 3

Upvotes: 0

Views: 3713

Answers (2)

Gordon
Gordon

Reputation: 20150

Or, if you need a count of the number of values whether or not they're distinct, you could use a custom reduce function, something like:

tempDim.groupAll().reduce(
    function(p,v) { return (v.temp !== undefined) ? p+1 : 0; },
    function(p,v) { return (v.temp !== undefined) ? p-1 : 0; },
    function() { return 0; })\

Then you can generalize using the reusable reduce function pattern.

Upvotes: 0

Ethan Jewett
Ethan Jewett

Reputation: 6010

Won't this get you the number of distinct temps and phs?

var tempDim = xFilter.dimension(function(d) {return d.temp;}); 
var tempGroup = tempDim.group();
console.log(tempGroup.top(Infinity).length);

var phDim = xFilter.dimension(function(d) {return d.pH;});
var phGroup = phDim.group()
console.log(phGroup.top(Infinity).length);

Upvotes: 1

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