d3js: time scaling and "1901" - javascript

I'm working with a time-based scatterplot and am using data which only parses times by month, hour and day. On my axis labels, I'm getting "1901". D3 seems to be choosing a year and displaying it. How can I easily get rid of this? I don't want any year displayed:
1901 example http://lmnts.lmnarchitects.com/wp-content/uploads/2014/04/2014-04-01-09_31_30-127.0.0.1_8020_Climate3_seattle-winter-temps.html.jpg

you need to set the tickFormat of your axis to display only months and days. The tickFormat receives a function that takes a date and returns a string. You can use d3.time.format to set the tick format:
var axis = d3.svg.axis()
// ... set more attributes
.tickFormat(d3.time.format('%b %d')); // Abbreviated month and decimal day (Apr 01)
Regards,

Related

How can I control the date format for d3 scaleTime and remove unwanted clock time ticks?

I'm trying to display a week's worth of data in an area chart, and would like to use scaleTime() to populate my x axis. I've converted the date strings to date objects, and the domain appears to be correct, but I can't get the x axis to display the format I want. What I would like to see are 7 tick marks with the day, month, and year displayed. Instead, I'm seeing the day of the week and the date, and there are additional tick marks displaying '12 PM', as in the attached picture.
I've tried specifying the number of tick marks, but then it gets even weirder, especially on month transitions, and might display something like 'Mon 29, Tues 30, Wed 31, November, Fri 2'.
Bottom line, am I missing something in how I'm implementing the scale, and if not, how might I go about fine-tuning the tick marks to only show what I want to see? The examples I've been able to find don't seem to run into the same problems I'm experiencing.
Current format of my date objects: "2020-07-22T06:00:00.000Z"
The code:
let x = d3.scaleTime().range([0, width-margin.right-margin.left])
let y = d3.scaleLinear().range([height-margin.bottom, margin.top])
x.domain([d3.min(area_data, d => d.date), d3.max(area_data, d=>d.date)])
y.domain([0, max_cases])
let xAxis = d3.axisBottom(x);
let yAxis = d3.axisLeft(y);
Thanks in advance.
You can do something like
const xAxis = d3.axisBottom(x)
.ticks(d3.timeDay.every(1), '%-d %b %Y');
The first argument to ticks says that you want one tick for each day. The second argument is a format specifier that defines how to format the dates as strings. '%-d %b %Y' shows the day with no padding, the abbreviated month name, and the full year. For example, 22 Nov 2021. You can modify this as needed to get your desired format.

nvd3 some xAxis ticks missing

I have an nvd3 line chart that needs to display every date in a month on the x axis. For the current month (July) I have generated 31 x,y pairs. However, the chart omits a couple of those data points. Most data points, actually, have the y coordinate set to null (because not all dates have data, but I still need to display every date).
This is how it looks now:
As you can see, there are some dates missing: 07/08/2018, 07/15/2018, 07/22/2018, 07/30/2018 and 07/31/2018.
This is my code:
chart.xAxis.ticks(weightData.length); // this is 31
chart.xAxis.rotateLabels(-35);
chart.xAxis.showMaxMin(false); // if this is true, even less data is displayed
Is there a way to force the chart do display all the data on the x axis?
I have found the answer here:
NVD3 Line Chart X Axis Ticks Are Missing
The point is to use tickValues() instead of ticks() as the answer on the post in link says.

D3js Changing ticks on Zoomable Time axis

Background
I have a zoomable time graph which I build incorporating the following code:
var x = d3.time.scale().range([0, 100]);
var xAxis = d3.svg.axis()
.scale(x)
.tickFormat(customformatter);
When the appropriate interval is years, it shows ticks of years. Months shows months, etc.
Problem
This works wonderfully, generating great ticks until I zoom down into weeks, at which point I need to be able to dictate what day of the week ticks show for (Sunday, monday, etc.). I am aware of the multiformat custom generator for tickFormat in which you can specify the format given the appropriate interval. That will not change the ticks, however. Is there a way to set the start of the weeks' rules while maintaining the tick generation that otherwise exists at the year, month, day (etc.) level? Can the default start date be set to some other day of the week for the d3 library?
This is hardly a recommendable answer to my own question, but if anyone is desperate one way is to override the source code in /src/time/week.js:
d3_time.week = d3_time.sunday;
d3_time.weeks = d3_time.sunday.range;
d3_time.weeks.utc = d3_time.sunday.utc.range;
d3_time.weekOfYear = d3_time.sundayOfYear;
Just swap out 'sunday' for another day of the week.

Show time durations on a d3 axis

I am currently creating a d3 axis using d3.time.scale.utc(). My input for the axis is a series of time offsets in minutes (with decimal values). For example:
var minuteOffsets = [0.03, 1.65, 3.22, ..., 89.91, 90.01];
I want to display these time offsets in mm:ss format on the axis. The axis labels can be at standard intervals, like so:
+------+------+-- ... --+------+------+-- ... --+------+
00:00 00:30 01:00 59:30 60:00 60:30 90:00 90:30
Note specifically that the minute value should show values >60. The seconds value has the normal range 0-59.
When I tried using .tickFormat(d3.time.format('%M:%S')), it wraps the minute value back to 00:00 after the 45:00 label. I also had a look at duration from moment.js, but I can't figure out how exactly to incorporate that into my code.
Based on the comment by Lars Kotthoff, I changed my scale to be a linear scale, instead of a time scale. Then I added a custom tickFormat function to do the necessary formatting.
I used MomentJS to first create a duration from the minute values, and then used the library moment-duration-format to produce the tick label in mm:ss format.
var axis = d3.svg.axis().tickFormat(function (d) {
return moment.duration(d, 'minutes')
.format('mm:ss', { trim: false });
});
This helps to avoid explicitly writing code for extracting the minute and second components, and then formatting them into a string.

Changing time scale from days to weeks, how do I update and sum data values?

I am trying to have my barchart in d3.js update it's values when the user changes the time scale from days, to weeks or months. (i.e. when the time scale is changed to weeks, I want all the data values for each day in a given week summed together). For example, here is the default graph with the x-axis time scale in days:
x-Axis in days
When a user changes the time scale to weeks and the x-axis updates, the data values remain grouped by day, as shown here:
x-Axis scale in weeks, but data values remain grouped by day:
What I want is for there to be only one bar for each week number of the year on the x-axis, showing the sum of all the data values the user provided for all 7 days of that week. How do I achieve this?
Does this have to be done on the server-side, or can it be on the client-side with javascript, or is there some easy d3.js way I'm overlooking?
This is what my data looks like:
[{"date":"2013-04-20","load_volume":400},{"date":"2013-04-23","load_volume":400},{"date":"2013-04-24","load_volume":400},{"date":"2013-04-28","load_volume":1732},{"date":"2013-04-30","load_volume":400}]
I figured to achieve this I could convert the date values to weekNumberOfYear format (for e.g., 17 for this week), push them into an array and remove all duplicates, then sum the data values for each of the days in that array. I did this and the data looked like this:
[{"date":"15","load_volume":400},{"date":"16","load_volume":2532},{"date":"17","load_volume":400}]
However, I don't believe this is the correct approach because I always get an "Error: Invalid value for attribute x="NaN"" in the JS console. This I think is because I use the x scale to position the rects on my graph:
.attr("x", function(d) { return padding + x(new Date(d.date)); })
... which would result in x(Wed Dec 31 1969 19:00:00 GMT-0500 (EST)), which throws a NaN error.
I am now trying to format the date into %Y-%m-%d format and have it be the beginning Monday of each week, but I'm wondering if there is an easier solution since I've been at this all day.
Well, I think I've figured it out. I just had to convert the dates to millisecond time and remove the double quotes I had around the date value in the JSON string (the double quotes were giving me a NaN error). I did this with the following function:
function getWeekDate(d) {
d = new Date(d); // get current date
var day = d.getDay();
var diff = d.getDate() - day + (day == 0 ? -6 : 1); // Subtract day number of month from day number of week, and adjust when day is sunday
var date = new Date(d.setDate(diff));
return date.setHours(0);
}
which is adapted from this SO question.
Not sure if D3 has a better way of doing it. If I find out i'll post it here.

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