How to filter out some extraneous columns from .csv for grouped bar chart?

[Maggie Lee]

I want to make a grouped bar chart, but my .csv has 20 columns. Only 4 have the data I need.  The other 16 columns I might need later, so I don't want to just open my .csv in Excel and kill the other 16 columns. 

I'm following the canonical example, and I think the answer is in these key lines, but I don't understand them.

http://bl.ocks.org/mbostock/3887051

d3.csv("data.csv", function(error, data) {
  var ageNames = d3.keys(data[0]).filter(function(key) { return key !== "State"; });

  data.forEach(function(d) {
    d.ages = ageNames.map(function(name) { return {name: name, value: +d[name]}; });
  });

How would one modify the code if data.csv had extraneous columns as so?

I suspect the logic will be something like "select the columns where column name includes "Years" or "State."

State,Under 5 Years,5 to 13 Years,14 to 17 Years,18 to 24 Years,25 to 44 Years,45 to 64 Years,6 Years and Over, Random_Four_Digit_Code, Commonest_Bird
CA,2704659,4499890,2159981,3853788,10604510,8819342,4114496, 0264, Crow
TX,2027307,3277946,1420518,2454721,7017731,5656528,2472223, 0693, Robin
NY,1208495,2141490,1058031,1999120,5355235,5120254,2607672, 1808, Bluebird

Thanks!

-Maggie

[Japhy Bartlett]

Probably want something like:

.filter(function(key) { return key == "Random_Four_Digit_Code" || key == "Commonest_Bird"; })

with the caveat that I'm not sure about the details of filter() offhand.  you could also make a copy of the csv that's stripped down to what you need - if you're serving this on a website, it will make the file smaller and the page load faster.

another route, in the .map() function, only return the columns you want!

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[Maggie Lee]

hey thanks that worked great!