datalib/src/format-tables.js

JavaScript utilites for loading, summarizing and working with data.

var util = require('./util'),
    type = require('./import/type'),
    stats = require('./stats'),
    template = require('./template');

module.exports = {
  table:   formatTable,  // format a data table
  summary: formatSummary // format a data table summary
};

var FMT = {
  'date':    '|time:"%m/%d/%Y %H:%M:%S"',
  'number':  '|number:".4f"',
  'integer': '|number:"d"'
};

var POS = {
  'number':  'left',
  'integer': 'left'
};

function formatTable(data, opt) {
  opt = util.extend({separator:' ', minwidth: 8, maxwidth: 15}, opt);
  var fields = opt.fields || util.keys(data[0]),
      types = type.all(data);

  if (opt.start || opt.limit) {
    var a = opt.start || 0,
        b = opt.limit ? a + opt.limit : data.length;
    data = data.slice(a, b);
  }

  // determine char width of fields
  var lens = fields.map(function(name) {
    var format = FMT[types[name]] || '',
        t = template('{{' + name + format + '}}'),
        l = stats.max(data, function(x) { return t(x).length; });
    l = Math.max(Math.min(name.length, opt.minwidth), l);
    return opt.maxwidth > 0 ? Math.min(l, opt.maxwidth) : l;
  });

  // print header row
  var head = fields.map(function(name, i) {
    return util.truncate(util.pad(name, lens[i], 'center'), lens[i]);
  }).join(opt.separator);

  // build template function for each row
  var tmpl = template(fields.map(function(name, i) {
    return '{{' +
      name +
      (FMT[types[name]] || '') +
      ('|pad:' + lens[i] + ',' + (POS[types[name]] || 'right')) +
      ('|truncate:' + lens[i]) +
    '}}';
  }).join(opt.separator));

  // print table
  return head + "\n" + data.map(tmpl).join('\n');
}

function formatSummary(s) {
  s = s ? s.__summary__ ? s : stats.summary(s) : this;
  var str = [], i, n;
  for (i=0, n=s.length; i<n; ++i) {
    str.push('-- ' + s[i].field + ' --');
    if (s[i].type === 'string' || s[i].distinct < 10) {
      str.push(printCategoricalProfile(s[i]));
    } else {
      str.push(printQuantitativeProfile(s[i]));
    }
    str.push('');
  }
  return str.join('\n');
}

function printQuantitativeProfile(p) {
  return [
    'valid:    ' + p.valid,
    'missing:  ' + p.missing,
    'distinct: ' + p.distinct,
    'min:      ' + p.min,
    'max:      ' + p.max,
    'median:   ' + p.median,
    'mean:     ' + p.mean,
    'stdev:    ' + p.stdev,
    'modeskew: ' + p.modeskew
  ].join('\n');
}

function printCategoricalProfile(p) {
  var list = [
    'valid:    ' + p.valid,
    'missing:  ' + p.missing,
    'distinct: ' + p.distinct,
    'top values: '
  ];
  var u = p.unique;
  var top = util.keys(u)
    .sort(function(a,b) { return u[b] - u[a]; })
    .slice(0, 6)
    .map(function(v) { return ' \'' + v + '\' (' + u[v] + ')'; });
  return list.concat(top).join('\n');
}