Counting Weekdays

weekday.js

weekday = (function() {

// Returns the weekday number for the given date relative to January 1, 1970.
function weekday(date) {
  var weekdays = weekdayOfYear(date),
      year = date.getFullYear();
  while (--year >= 1970) weekdays += weekdaysInYear(year);
  return weekdays;
}

// Returns the date for the specified weekday number relative to January 1, 1970.
weekday.invert = function(weekdays) {
  var year = 1970,
      yearWeekdays;
 
  // Compute the year.
  while ((yearWeekdays = weekdaysInYear(year)) <= weekdays) {
    ++year;
    weekdays -= yearWeekdays;
  }
 
  // Compute the date from the remaining weekdays.
  var days = weekdays % 5,
      day0 = ((new Date(year, 0, 1)).getDay() + 6) % 7;
  if (day0 + days > 4) days += 2;
  return new Date(year, 0, (weekdays / 5 | 0) * 7 + days + 1);
};

// Returns the number of weekdays in the specified year.
function weekdaysInYear(year) {
  return weekdayOfYear(new Date(year, 11, 31)) + 1;
}

// Returns the weekday number for the given date relative to the start of the year.
function weekdayOfYear(date) {
  var days = d3.time.dayOfYear(date),
      weeks = days / 7 | 0,
      day0 = (d3.time.year(date).getDay() + 6) % 7,
      day1 = day0 + days - weeks * 7;
  return Math.max(0, days - weeks * 2
      - (day0 <= 5 && day1 >= 5 || day0 <= 12 && day1 >= 12) // extra saturday
      - (day0 <= 6 && day1 >= 6 || day0 <= 13 && day1 >= 13)); // extra sunday
}

return weekday;

})();

Hi Mike! There is a bug in weekday.invert function:

> weekday.invert(11000);
< Fri Mar 02 2012 00:00:00 GMT+0300

> weekday(weekday.invert(11000);
< 11001

Invert function result is off by +1 day in case when the first day of the year lands on Sunday. This is the case of 2012.
The bug is in line 25:

if (day0 + days > 4) days += 2;

The fix is to add the check right after line 25:

if (day0 === 6) days -= 1;

I have successfully tested the fix this way:

> d3.range(10000).every(d => d === weekday(weekday.invert(d)));
< true

Hey Mike, sorry for posting on wrong thread. But my issue is related to d3.scaleLinear/d3.scaleTime. We are using D3 V4. Need to display date on x-axis and number on Y-axis. When set x-axis values to domain and specify ticks(5), I am facing 2 issues mentioned below.

1. Sometimes ticks are more than 5 which I understood from D3 api that it is a limitation. This issue was addressed by using tickSize.
2. But I am seeing dates on x-axis which are not in the input object. For example, I have dates 01/31, 02/01, 02/02, 02/05 and 02/06 (weekend dates were excluded), but x-axis is showing dates 02/03 and 02/04 which is not acceptable for my business.

Could you please us a direction to overcome this issue? Our organization just started using D3 so we have less help from our IT teams.

Hello,
It is awesome job but I cannot find a graph with Time frame such as H1, H4, D1, W1, M1.
Do you have plan to develop this sample ?
I need to know that How the Lib is support multiple time frame ?
And How we make UI tool overlay on graph area ?
if it able to support please let me know at [email protected]
I have a project that need your help with good wage if you interest.
Thank you,
Rocky