81 articles tagged #Data Analysis
When you run str.split() on a Pandas column, rows that don't contain the delimiter come back as NaN and quietly disappear from your results. Here's exactly why it happens and how to fix it without losing a single row.
You run value_counts() on a column, get a clean frequency table, and only later realize your NaN values were silently dropped. Here's exactly why it happens and how to fix it without losing your missing data signal.
You called dropna() to keep only fully complete rows, but it's quietly dropping rows that still have useful data. Here's exactly why that happens and the parameters you need to get complete-case filtering right.
When pandas apply() swallows row-level exceptions without warning, your pipeline keeps running while corrupt results pile up silently. Here's how to detect, debug, and prevent this behavior for good.
When pd.to_datetime() quietly turns valid dates into NaT, your analysis is already broken — and you may not notice until much later. Here's exactly why it happens and how to fix it cleanly.
Pandas groupby silently drops None keys by default, leaving your aggregations short and your results confusing. Here's exactly why it happens and how to fix it in three reliable ways.
Excel MATCH returns #N/A even when the value clearly exists in your list — and the culprit is almost always a type mismatch. Numbers stored as text look identical but behave differently. Here's how to diagnose and fix it fast.
COUNTIFS returning zero even though matching rows clearly exist? The most common culprit is mismatched criteria range sizes. Here's exactly how to diagnose and fix it in under five minutes.
XLOOKUP's approximate match modes are more nuanced than VLOOKUP's. If your formula keeps returning #N/A even though the lookup value clearly exists in a nearby range, the match mode and sort order are almost certainly the culprits.
Your INDEX MATCH formula looks right, but sorted data is feeding it wrong results. This guide breaks down the exact reason it happens and shows you the precise fix — no helper columns needed.
INDIRECT is powerful for dynamic references, but one wrong character in the sheet name and you get a #REF! error that's maddeningly hard to debug. Here's exactly what causes it and how to fix it for good.
Your SUMIFS formula looks right, but the moment you point a criteria range or criteria value at another sheet, it returns zero. Here's why that happens and exactly how to fix it.