Subscript & Indexing Errors
Undefined columns selected
Matches: undefined columns selected
WHAT THIS ERROR MEANS
You tried to select a column that doesn't exist in your data frame, usually due to a typo or wrong column name.
HOW TO FIX IT
1. Check available columns with names(df) or colnames(df).
2. Look for typos in the column name.
3. Remember column names are case-sensitive.
CODE EXAMPLES
BAD — THIS CAUSES THE ERROR
df[, "Sepal.length"] # wrong case
GOOD — CORRECT APPROACH
df[, "Sepal.Length"] # correct case
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