Apprendre Conditional Transformations of Data Columns

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Definition

Conditional transformations are operations where you modify the values in a data column only when certain criteria are met. In exploratory data analysis (EDA), these transformations help you flexibly recode, flag, or adjust data points based on specific conditions, enabling targeted insights or data cleaning.

When working with data, you often need to change column values only if they meet certain criteria. This approach allows you to apply functions or set new values in a column, but only for rows where a condition holds true. Conditional transformations are especially useful for handling outliers, recoding categories, or creating new flags based on thresholds. In R, you can use logical conditions combined with assignment or transformation functions to accomplish this. The most common way is to use logical indexing or the ifelse() function, which evaluates a condition for each row and assigns a value accordingly. This method helps you keep your data tidy and analysis-ready by ensuring that only the relevant values are changed, while others remain untouched.


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# Suppose you have a data frame of exam scores
scores <- data.frame(
  student = c("Alice", "Bob", "Carol", "David"),
  math = c(92, 67, 88, 45)
)

# You want to label scores below 70 as "Fail" and 70 or above as "Pass"
scores$math_result <- ifelse(scores$math >= 70, "Pass", "Fail")

print(scores)

Conditional transformations are common in scenarios such as recoding categorical variables, flagging unusual values, or creating new columns for further analysis. Best practices include keeping your conditions clear and readable, using vectorized functions like ifelse() for efficiency, and avoiding overwriting original data unless necessary. Always validate the results of your transformation by checking a sample of the output or using summary statistics to ensure your logic has been applied correctly. This approach makes your EDA workflow more robust and adaptable to a wide range of analytical questions.

1. Which R expression correctly labels each score as "Pass" if it is 70 or above, and "Fail" otherwise, for every row in the `scores` data frame

2. Complete the code to create a new column in the `scores` data frame that labels each math score as "Pass" if it is 70 or above, and "Fail" otherwise, using the `ifelse()` function.

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Section 1. Chapitre 27

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Section 1. Chapitre 27

Conditional Transformations of Data Columns

1. Which R expression correctly labels each score as "Pass" if it is 70 or above, and "Fail" otherwise, for every row in the scores data frame

2. Complete the code to create a new column in the scores data frame that labels each math score as "Pass" if it is 70 or above, and "Fail" otherwise, using the ifelse() function.

1. Which R expression correctly labels each score as "Pass" if it is 70 or above, and "Fail" otherwise, for every row in the `scores` data frame

2. Complete the code to create a new column in the `scores` data frame that labels each math score as "Pass" if it is 70 or above, and "Fail" otherwise, using the `ifelse()` function.