Can you build a mobile calendar picker?

It was Natalia Miteva‘s turn to post the #WOW2020 challenge this week. It’s a parameter actions based challenge, inspired by a date range picker viz originally posted by Ludovic Tavernier.

Once again, I found this week tough! I understand the concept of parameter actions, and can use them for the ‘basics’, but the funky stuff people come up with to bend them to their will, is really beyond me.

I started the challenge with good intentions as always, ‘relating’ the Dates data to the Superstore data set matching the Date field to the Order Date field, built out the calendar view, but got stuck trying to figure out how to set the parameter action into an ‘End Date’ parameter, when I was already setting a ‘Start Date’ parameter. After staring at the screen for some time, I figured I’d try to work it all out from Ludovic’s viz instead.

There’s A LOT going on in this challenge, so I’ll do my best to explain.

  • Building the Calendar Picker
  • Building the Next / Previous control
  • Building the Year/Month control
  • Building the KPI & Trend Chart

Building the Calendar Picker

The calendar will only show 1 month, so let’s deal with that to start with.

A parameter will be used to store a date related to the month to show.


This is a date parameter that I chose to default to 01 June 2019.

Month Date


This is truncating every Date in the dataset to the 1st of the relevant month

Month To Show

[pMonthSelected] = [Month Date]

Add this to the Filter shelf and set to True will limit the data to a single month, June 2019 by default.

To display the days of the month in the ‘grid’ layout, we need to know the day of the week each day falls on (so we know what column to position the day in), and we need to know what week in the year the day falls in, as this will dictate which row to position the day in.

Day of Week (Abbrev)

LEFT(DATENAME(‘weekday’, [Date]),3)

The basic calendar layout can then be built by

  • Month To Show = True on Filter
  • Day of Week (Abbrev) on Columns
  • WEEK(Date) on Rows
  • DAY(Date) on Text

The WEEK(Date) field is then hidden.

We’re going to need to represent each day by a ‘square’ block. I achieve this by adding MIN(1) to Columns, changing the mark type to Bar, fixing the axis from 0-1, then hiding the axis.

So now the basic calendar layout is achieved, we need to figure out how to select a start & end, and colour accordingly.

We’re going to use a single string parameter to store both the selected start & end dates, using a | to act as a delimiter allowing us to identify & so separate the 2 dates.


String parameter set to empty string by default

Show the parameter on the viz, and I will attempt to walk through the steps, showing how the values in the parameter influence other fields and what is displayed on the viz.

We need another field, that is going to be used in conjunction with the parameter. I’m going to build up what this field needs to store as we go through, so hoping it will all make sense.

Date Control

IF [pSelectedDates]=”” THEN STR([Date]) END

If the parameter is empty, then set Date Control to be the date.

Let’s add this to the Text so you can see what happens to this field.

So the first action we expect the user to take is to click on a single date displayed. This value stored in the Date Control field will be passed via the parameter action into the pSelectedDates field (I’ll show you how this works later). For now let’s assume the user has clicked on the 5th June, so type 2019-06-05 into the pSelectedDates field.

This is now the start date, and we need the Date Control field to change to reflect this

Date Control

IF [pSelectedDates]=”” THEN STR([Date])
ELSEIF [Date]<=DATE([pSelectedDates]) THEN STR([Date])
ELSE [pSelectedDates]+”|”+STR([Date]) END // else store start & end date

If the Date displayed is before that stored in the parameter, then Date Control will continue just to store the date, otherwise it will append | followed by the date onto the existing parameter value.

So when a date is clicked again, the value of the Date Control will once again be passed to the pSelectedDates parameter.

If the date clicked is earlier than the one already stored, eg let’s say 04 June was clicked, the Date Control value of 04 June is passed to the parameter, and is now the ‘start date’. Type 2019-06-04 into the pSelectedDates field.

But if a later date is selected, say 18th June, the Date Control value of 2019-06-04|2019-06-18 is passed into the pSelectedDates parameter, and we now need another step with our Date Control field :

Date Control

IF [pSelectedDates]=”” THEN STR([Date])
ELSEIF CONTAINS([pSelectedDates],”|”) THEN STR([Date])
ELSEIF [Date]<=DATE([pSelectedDates]) THEN STR([Date])
ELSE [pSelectedDates]+”|”+STR([Date]) END

The 2nd statement is now looking for the | character and if it finds it, we know a start & end dates has been selected, so we need to ‘reset’ this control field to how it was originally – just it’s own date.

Type in 2019-06-04|2019-06-18 into the pSelectedDates field to see this.

Ok, so now we can see how the pSelectedDates field is working with the Date Control field, we now need to define some additional fields to help us identify the start & end of the dates selected, so we can work out what to colour.

Date Selection Start


This is looking for the position of the | field and taking everything from the first character in the pSelectedDates string up to the character before the |.

Note I originally used DATE(SPLIT([pSelectedDates], “|”,1)), but after extracting the data set, this calculation caused errors. I don’t know why, but the above workaround sufficed.

Date Selected End

DATE(MID([pSelectedDates], FIND([pSelectedDates],”|”)+1,10))

Find the position of the | and take all the characters starting at the position after the | and ending at the character 10 characters later (the date format is 10 characters so this can be easily hardcoded)


IF [Date]= [Date Selection Start] OR [Date] = [Date Selection End] THEN ‘Hot Pink’
ELSEIF [Date] > [Date Selection Start] AND [Date] < [Date Selection End] THEN ‘Pink’
ELSE ‘White’

Add this onto the Colour shelf, and adjust accordingly

We can remove the Date Control from Text now, but it needs to remain in the view, so it can be referenced when we build the parameter action. Add it onto Detail shelf instead.

Finally add this viz onto a dashboard, then add the parameter action, setting the Target Parameter to pSelectedDates and the Field to pass as Date Control.

As you play around selecting values on the dashboard, you’ll notice the dates appear ‘greyed out’, as the ‘on click’ action is essentially highlighting what you’ve selected. To stop this from happening create a calculated field called True that just stores the value of True and and a calculated field called False that stores the value False. Add both of these to the Detail shelf of the calendar viz.

Then on the dashboard, add a Filter action that goes from the dashboard to the sheet itself, passing the values Source: True = Target: False

Building the Next / Previous Control

We need to store the value of the next month related to the Date unless we’re already in the last month of the data set, in which case we’ll just keep the same month (ie if the month is 01 Nov 2019, next month will be 01 Dec 2019, but if the month is 01 Dec 2019 which is the last month in the data set, the next month will also be 01 Dec 2019. This stops the next control from moving forward when we reach the end.

Next Month

IF [Month Date] = {MAX([Month Date])} THEN [Month Date] ELSE
DATE(DATEADD(‘month’, 1, [Month Date]))

Change the mark type to Shape and select an appropriate arrow. If need be reduce the transparency of the shape colour (I chose 50% which changed a black arrow to look like a grey arrow).

On a new sheet, Add Month To Show = True to the Filter shelf, and Next Month to the Detail shelf.

If you recall, right at the start, we created a pMonthSelected parameter, and this will be used to change the month displayed.

Add the viz to the dashboard, and add a parameter action that on select, targets the pMonthSelected parameter, passing in the Next Month field

For the Previous Month control, we need apply similar steps, but using the field below instead.

Prev Month

IF [Month Date] = {MIN([Month Date])} THEN [Month Date] ELSE
DATE(DATEADD(‘month’, -1, [Month Date]))

Building the Year/Month control

When building the Year selector, we need to filter the data to just the month name already selected/in view, which is based on the pMonthSelected parameter. Ie if the month selected is 01 June 2019, we want the data related to June 2016, June 2017, June 2018, June 2019

Filter Month


Add this to the Filter shelf, set to true, then build out the view as below, fixing the axes between 0-1 again, and then hiding. You can see the values of the Month(Date)) displayed, and it’s this field that will be passed via a parameter action. It can be moved to Detail.

COLOUR:Selected Year


Add this to the Colour shelf and adjust accordingly.

When added to the dashboard, the associated parameter action required is :

When building the month selector, we need a similar filter to ensure the months shown are all associated to a single year

Filter Year

YEAR([pMonthSelected]) = YEAR([Date])

Add this to the Filter shelf set to True.

The layout of the Months, requires some additional fields to determine which row and column the month should be positioned in.

Month Cols

IF (DATEPART(‘month’,[Date]) %4) =0 THEN 4
ELSE (DATEPART(‘month’,[Date]) %4)

DATEPART returns the integer value of the month, ie a number between 1-12, so this calculation is using the modulo (%) function to position based on the remainder when dividing the month number by 4.

Month Row

IF DATEPART(‘month’,[Date]) <=4 THEN 1
ELSEIF DATEPART(‘month’,[Date]) <= 8 THEN 2

Adding these to the view as follows gives us a grid

Note the blue Month(Date) on the Text shelf is showing just the month name ie ‘January’, and has been formatted to it’s abbreviation. The green Month(Date) on the Detail shelf is storing the full month year ie January 2019.

COLOUR:Selected Month

[pMonthSelected]=[Month Date]

Add to the colour shelf and adjust accordingly.

You can then hide the Month Col & Month Row fields from displaying.

When added to the dashboard, the associated parameter action required is

Note You will need to apply the same ‘true=false’ trick described earlier to both these views using filter actions to prevent them from highlighting on selection.

Hiding the year/month selector

On the dashboard add a vertical container, then place the Year Selector sheet and the Month Selector inside.

Remove the chart titles, set the background of the container to white, then set the container to be floating and select the container option to Add Show/Hide Button.

You’ll need to spend some time adjusting the size and the position of the floating container once you have the layout of all the other objects finalised.

Building the KPI & Trend Chart

I’m going to try to be brief with this section. The above is A LOT to take in and write!

Selected Period

This is simply using the Date Selection Start & Date Selection End fields to display in a text field


We need to be able to filter the data being displayed based on the selection

Dates to Show

[Date]>= [Date Selection Start] AND [Date]<= [Date Selection End]

This is added to the Filter shelf and set to True.

After that we’re just building a simple Text based viz utilising Measure Names & Measure Values as shown below

And finally the trend chart, again needs to be filtered by Dates To Show = True, and is a simple line chart plotting Date against the measures required as below

When added to the dashboard, these 2 sheets should be placed side by side in a horizontal container, both set to fit entire view. The right padding should be set to 0 for the KPI chart and the left padding set to 0 for the trend chart. This will have the effect of the horizontal lines for each chart joining together to make it look like a single chart.

Phew! I’m beat! My published viz is here. Keeping fingers crossed for a challenge that is easier to blog about next week 🙂

Happy vizzin’! Stay Safe!


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s