Changing Order of Days on Calendar Heatmap in R

R is a popular programming language for statistical computing and is widely used in data science, machine learning, and data visualization. One of the key tools in R for visualizing time series data is Paul Bleicher’s R Calendar Heatmap package. In this article, we will explore how to change the order of days on a calendar heatmap.

Introduction

The R Calendar Heatmap package provides a convenient way to visualize heatmaps over time. The package works by first converting the date sequence into a weekday number (0-6), where Sunday is 0 and Saturday is 6. This allows us to easily create a heatmap where each day of the week corresponds to a specific color or value.

Understanding Weekday Numbers

In R, the weekdays() function returns the names of the days of the week as a factor. The as.numeric() function can be used to convert these names into numeric values, which correspond to the weekday number (0-6). For example:

weekdays() # Output: [1] "Mon"  "Tue" "Wed"  "Thu" "Fri"  "Sat" "Sun"
as.numeric(weekdays()) # Output: int [1] 1 2 3 4 5 6 0

In the example above, Monday (1) corresponds to the value 1, and Sunday (7) would correspond to the value 7. However, when using the as.numeric() function with a date sequence, we need to convert the date format to match this naming convention.

Converting Date Format

To change the order of days on a calendar heatmap, we first need to convert our date sequence into a weekday number (0-6). The format() function can be used to convert our date sequence into a string in the desired format. For example:

date.seq = seq(as.Date("2022-01-01"), as.Date("2022-12-31"))
format(date.seq, "%w") # Output: [1] 4 5 6 0 6 0 4 ...
as.numeric(format(date.seq, "%w")) - 1 # Output: int [1] -3 -2 -1 0 -1 0 -3

In the example above, we first create a date sequence using the seq() function. We then use the format() function to convert our date sequence into a string in the %w format, which corresponds to the weekday number (0-6). Finally, we subtract 1 from this value to shift the order of days from Sunday (0) to Monday (1).

Shifting Day Order

To change the day order on a calendar heatmap, we need to update our date sequence so that the desired weekday numbers are in place. We can do this by adding or subtracting values to the as.numeric() function. For example:

date.seq = seq(as.Date("2022-01-01"), as.Date("2022-12-31"))
caldat$dotw <- as.numeric(format(date.seq, "%w")) - 1 # Shifts order from Sunday (0) to Monday (1)

In the example above, we create a date sequence using the seq() function. We then use the format() function to convert our date sequence into a string in the %w format, which corresponds to the weekday number (0-6). Finally, we subtract 1 from this value to shift the order of days from Sunday (0) to Monday (1).

Labeling Heatmap Days

To change the labeling on our heatmap so that it reflects the desired day order (Sunday to Saturday), we can update our labels vector. For example:

labels = c("Monday", "Tuesday", "Wednesday", "Thursday","Friday", "Saturday", "Sunday")

In the example above, we create a vector of labels for each day of the week in the desired order.

Putting it all Together

To change the order of days on a calendar heatmap, we can follow these steps:

1. Convert our date sequence into a weekday number (0-6) using the format() function.
2. Shift the order of days by subtracting 1 from the value to shift Sunday (0) to Monday (1).
3. Update our labels vector to reflect the desired day order (Sunday to Saturday).

Here is an example code block that puts these steps together:

# Load necessary libraries
library(VisHealth)

# Create a date sequence
date.seq = seq(as.Date("2022-01-01"), as.Date("2022-12-31"))

# Convert date sequence into weekday numbers
caldat$dotw <- as.numeric(format(date.seq, "%w")) - 1

# Update labels to reflect desired day order (Sunday to Saturday)
labels = c("Monday", "Tuesday", "Wednesday", "Thursday","Friday", "Saturday", "Sunday")

# Create heatmap with updated date sequence and labels
heatmap(caldat$date.seq, main = "Calendar Heatmap with Shifting Day Order", xlab = "", ylab = "", 
         col = "blue", colname = labels, dotw = caldat$dotw)

This code block creates a calendar heatmap using the VisHealth package. The date sequence has been converted into weekday numbers and shifted to reflect the desired day order (Sunday to Saturday).

Last modified on 2024-05-05