How to Calculate Elapsed Time Between Consecutive Measurements in a DataFrame with R and Dplyr

Here’s the complete code with comments and explanations:

# Load required libraries
library(dplyr)
library(tidyr)

# Assuming df1 is your dataframe

# Group by ID, MEASUREMENT, and Step
df %>% 
  group_by(ID, MEASUREMENT) %>% 
  # Calculate ElapsedTime as StartDatetime - lag(EndDatetime)
  mutate(ElapsedTime = StartDatetime - lag(EndDatetime)) %>% 
  # Replace all NA in ElapsedTime with 0 (since it's not present for the first EndDatetime)
  replace_na(list(ElapsedTime = 0))

Explanation:

group_by function groups your data by ID, MEASUREMENT, and Step. This is necessary because we want to calculate the elapsed time between each EndDatetime and its previous one.
The mutate function adds a new column called ElapsedTime to our dataframe. We use the formula StartDatetime - lag(EndDatetime) here. The lag function in R returns the value of a row that is a specified number of rows before the current row, by default 1. So, lag(EndDatetime) gives us the previous EndDatetime.
Finally, we use replace_na to replace all NA values in our ElapsedTime column with 0. Since it’s not present for the first EndDatetime, these NA values are replaced with 0.

This will give you your desired output!

Last modified on 2024-12-18