# Average Patient Wait Times

Erica set this challenge this week to provide the ability to compare the average wait time for patients in a specific hour on a specific day, against the ‘overall average’ for the same day of week, month and hour.

As with most challenges, I’m going to first work out what calculations I need in a tabular form, and then I’ll build the charts.

• Building the Calculations
• Building the Wait Time Chart
• Building the Patient Count Chart

Building the Calculations

The Date field contains the datetime the patient entered the hospital. The first step is to create a field that stores the day only

Date Day

DATE(DATETRUNC(‘day’,[Date]))

From this I could then create a parameter

Choose an Event Date

date parameter, defaulted to 6th April 2020, and custom formatted to display in dddd, d mmmm yyyy format. Values displayed were a list added from the Date Day field.

I also created several other fields based off of the Date field:

Month of Date

DATENAME(‘month’,[Date])

if the Date is Friday, 10 April 2020 16:53, then this field returns April.

Day of Date

DATENAME(‘weekday’,[Date])

if the Date is Friday, 10 April 2020 16:53, then this field returns Friday.

Hour of Date

DATEPART(‘hour’, [Date])

if the Date is Friday, 10 April 2020 16:53, then this field returns 16. I added this to the Dimensions (top half) of the data pane.

The viz being displayed only cares about data related to the day of the week and the month of the date the user selects, so we can also create

Records to Keep

DATENAME(‘weekday’, [Choose an Event Date]) = [Day Of Date]
AND
DATENAME(‘month’, [Choose an Event Date]) = [Month of Date]

On a new sheet, add this to the Filter shelf and set to True. When Choose an Event Date is Monday, 06 April 2020, then Records To Keep will ensure only rows in the data set relating to Mondays in April will display. Let’s build this.

Add Hour of Date, Day of Date, Month of Date to Rows, and then also add Date as a discrete exact date (blue pill).

You can see that all the records are for Monday and April. And by grouping by Hour of Date, you can see how many ‘admissions’ were made during each hour time frame. Remove Day of Date and Month of Date – these are superfluous and I just added so we could verify the data is as expected.

The measures we need are patient count and patient wait time. I created

Count Patients

COUNTD([Patient Id])

(although the count of the dataset will yield the same results).

Add Count Patients and Patient Waittime into the table.

This is the information that’s going to help us get the overall average for each hour (the line chart data). But we also need to get a handle on the data associated to the date the user wants to compare against (the bar chart).

Count Patients Selected Date

COUNTD(IF [Choose an Event Date] = [Date Day] THEN [Patient Id] END)

Wait Time Selected Date

IF [Choose an Event Date] = [Date Day] THEN [Patient Waittime] END

Add these onto the table – you’ll need to scroll down a bit to see values in these columns

So what we’re aiming for, using the hour from 23:00-00:00 as an example: There are 3 admissions on Mondays in April during this hour, 2 of which happen to be on the date we’re interested in. So the overall average is the sum of the Patient Waittime of these 3 records, divided by 3 (650.5 / 3 = 216.83), and the average for the actual date (6th April) in that hour is the sum of the Wait Time Selected Date for the 2 records, divided by 2 (509.5 / 2 = 254.75).

If we remove Date from the table now, we can see the values we need, that I’ve referenced above.

So let’s now create the average fields we need

Avg Wait Time

SUM([Patient Waittime])/[Count Patients]

Avg Wait Time Selected Date

SUM([Wait Time Selected Date]) / [Count Patients Selected Date]

Pop these into the table

This gives is the key measures we need to plot, but we need some additional fields to display on the tooltips.

Avg Wait Time hh:mm

[Avg Wait Time]/24/60

This converts the value we have in minutes as a proportion of the number of minutes in a day. Apply a custom number format of h”h” mm”mins”

Do the same for

Avg Wait Time Selected Date hh:mm

[Avg Wait Time Selected Date]/24/60

Apply a custom number format of h”h” mm”mins”

For the tooltip we need to show the hour start/end.

TOOLTIP: Hour of Date From

[Hour of Date]

custom format this to 00.00

TOOLTIP: Hour of Date To

IF [Hour of Date] =23 THEN 0
ELSE [Hour of Date]+1
END

custom format this to 00.00.

We can now start building the charts.

Building the Wait Time Chart

On a new sheet, add Records To Keep = True to the Filter shelf. Add Hour of Date as continuous dimension (green pill) to Columns and Avg Wait Time Selected Date to Rows. Change the mark type to Bar.

Then add Avg Wait Time to Rows and change the mark type of this measure to Line. Make the chart dual axis, synchronise the axis and adjust the colours of the Measure Names legend.

Add TOOLTIP: Hour of Date From and TOOLTIP: Hour of Date To and Avg Wait Time Selected Date hh:mm to the Tooltip of the bar marks card, and adjust the tooltip accordingly.

Add TOOLTIP: Hour of Date From, TOOLTIP: Hour of Date To, Avg Wait Time hh:mm, Day of Date and Month of Date to the Tooltip of the line marks card, and adjust the tooltip accordingly.

Remove the right hand axis. Remove the title of the bottom axis. Change the title on the left hand axis. Hide the ‘9 nulls’ indicator (right click). Remove column gridlines, all zero lines, all row and column dividers. Keep axis rulers. Format the numbers on the x-axis.

Change the data type of the Hour Of Date field to be a decimal, then edit the x-axis and fix to display from -0.9 to 23.9.

Amend the title of the chart to match the title on the dashboard.

Building the Patient Count Chart

On a new sheet, add Records To Keep = True to Filter, Hour of Date as continuous dimension to Columns and Count Patients Selected Date to Rows. Change Mark Type to Bar.

Right click on the y-axis and edit the axis. Remove the title, and check the Reversed checkbox to invert the axis. Edit the x-axis and fix from -0.9 to 23.9 as before.

Add TOOLTIP: Hour of Date From and TOOLTIP: Hour of Date To to the Tooltip and adjust accordingly.

Set the colour of the bars to match the same blue of the bars in the wait time chart, then adjust the opacity to 50%.

Remove all gridlines and zero lines. Retain axis ruler for both row and columns. Retain row divider against the pane only. Hide the x-axis.

We need to display a label for ‘Number of Patients’ on this chart. We will position it based on the highest value being displayed (rather than hardcoding a constant value). For this we create a new calculated field

Ref Line

WINDOW_MAX([Count Patients Selected Date]) +1

This returns the maximum value of the Count Patients Selected Date field, adds 1 and then ‘spreads’ that value across all the ‘rows’ of data.

Add this field to the Detail shelf. Then right click on the y-axis and Add Reference Line.

Add the reference line based on the average of the Ref Line field, and label it Number of Patients. Don’t show the tooltip, or display any line.

Once added, then format the reference line, and adjust the size and position of the text.

The sheets can now be added to a dashboard, placing them above each other. They should both be set to Fit Entire View. The width of the y-axis on the Patient Count chart will need to be manually adjusted so it is in line with the Wait time chart, and ensures the Hour columns are aligned..

My published viz is here.

Happy vizzin’!

Donna