84 articles tagged #Data Analysis
Pandas groupby() is one of the most powerful tools for data aggregation, but subtle issues such as missing values, duplicate keys, incorrect aggregation functions, or dropped categories can silently produce incomplete results. Learn how to identify and prevent silent data loss in your groupby
Your INDEX MATCH formula looks correct, but it keeps returning #N/A whenever the lookup value starts with a zero. The culprit is almost always a data-type mismatch between text and numbers — here's exactly how to diagnose and fix it.
SUMIFS returning a suspiciously low or incorrect total? If your sum range has merged cells, Excel is only reading the top-left cell of each merge — silently ignoring the rest. Here's how to find and fix it.
Your HAVING clause looks correct but keeps dropping groups you know should be there. This guide breaks down every common reason HAVING silently eliminates valid rows — NULLs, type mismatches, WHERE vs HAVING confusion — and shows you exactly how to fix each one.
Your CASE WHEN logic looks correct, but the column keeps coming back NULL. This happens more often than you'd expect, and the root causes are almost always subtle — mismatched types, NULL comparison traps, or a missing ELSE clause silently swallowing rows.
Your SUMIFS formula looks correct but keeps returning zero. The culprit is often numbers stored as text in your sum range — a silent data type mismatch Excel won't warn you about. Here's how to find and fix it fast.
Your Tableau dashboard looks complete, but certain rows keep disappearing without any error. If your data spans multiple time zones, a quiet UTC offset mismatch in date filters is likely the culprit. Here's how to catch and fix it.
Your SUMPRODUCT formula looks right, but it keeps returning zero — and the only thing unusual about your sheet is a handful of merged cells in the criteria column. Here's exactly why that happens and how to fix it.
Your SUMIFS formula looks right, but it returns zero the moment you swap a cell reference for an array constant like {"North","South"}. Here's exactly why that happens and four reliable ways to fix it.
Your SUMIFS formula looks correct, but it keeps returning zero whenever you use date criteria. The culprit is almost always text-formatted date cells that Excel refuses to compare as real dates. Here's how to diagnose and fix it fast.
Your SUMIFS formula looks correct, but it's pulling in rows you never intended — rows where the criteria cell is blank or holds a number stored as text. Here's exactly why mixed data types trip up SUMIFS and how to fix it.
Getting a #VALUE! error from XLOOKUP when your return array spans multiple columns? This is a common spill behavior trap. Learn exactly why it happens and how to fix it in a few keystrokes.