https://datanemics.com/ A crash course, a dataset library, and a browser-based visualization toolkit for people who work with data. Written by practising data engineers, analysts and scientists. en Sat, 08 Aug 2026 12:00:00 GMT https://datanemics.com/blog/the-overall-average-hides-8-different-numbers-2026/ https://datanemics.com/blog/the-overall-average-hides-8-different-numbers-2026/ Sat, 08 Aug 2026 12:00:00 GMT Real group means for one column across 8 segments, and what the pooled average conceals. statistics practice https://datanemics.com/blog/a-essentially-none-correlation-and-what-it-is-not-2026-08/ https://datanemics.com/blog/a-essentially-none-correlation-and-what-it-is-not-2026-08/ Fri, 07 Aug 2026 12:00:00 GMT A measured correlation of -0.00 between two columns, what its square says, and the diagnostic that costs one line. statistics https://datanemics.com/blog/what-3-500-job-postings-say-about-city/ https://datanemics.com/blog/what-3-500-job-postings-say-about-city/ Thu, 06 Aug 2026 12:00:00 GMT One column of a postings dataset, and what the shape of it means for anyone reading listings. career practice https://datanemics.com/blog/correction-as-of-feature-computation/ https://datanemics.com/blog/correction-as-of-feature-computation/ Wed, 05 Aug 2026 12:00:00 GMT The page claimed more than it should have. What it says now, and where the pattern stops applying. quality practice https://datanemics.com/blog/how-much-statistics-do-i-actually-need/ https://datanemics.com/blog/how-much-statistics-do-i-actually-need/ Tue, 04 Aug 2026 12:00:00 GMT Less theory than you fear, and more discipline than you would like. statistics career https://datanemics.com/blog/why-there-is-no-analytics-on-this-site/ https://datanemics.com/blog/why-there-is-no-analytics-on-this-site/ Mon, 03 Aug 2026 12:00:00 GMT No analytics, no tag manager, no cookie banner, because there are no cookies to consent to. practice https://datanemics.com/blog/charting-revenue-usd-by-device/ https://datanemics.com/blog/charting-revenue-usd-by-device/ Sun, 02 Aug 2026 12:00:00 GMT Two facts about the columns decide the chart. Cardinality and skew, in that order. visualization https://datanemics.com/blog/9-9-plus-or-minus-what/ https://datanemics.com/blog/9-9-plus-or-minus-what/ Sat, 01 Aug 2026 12:00:00 GMT A point estimate of 9.9%, the interval around it, and what a tighter one would cost. statistics https://datanemics.com/blog/a-five-minute-use-for-experiment-calculator/ https://datanemics.com/blog/a-five-minute-use-for-experiment-calculator/ Fri, 31 Jul 2026 12:00:00 GMT Sample size before you launch, and a confidence interval after you stop. Both directions, with the assumptions written on the screen rather than buried in a footnote. visualization https://datanemics.com/blog/saas-subscriptions-in-one-paragraph/ https://datanemics.com/blog/saas-subscriptions-in-one-paragraph/ Thu, 30 Jul 2026 12:00:00 GMT Twenty-five hundred B2B subscription accounts with signup dates, plans, seat counts, MRR and churn dates. quality practice https://datanemics.com/blog/cutting-a-lesson-down-designing-an-experiment-that-can-succeed/ https://datanemics.com/blog/cutting-a-lesson-down-designing-an-experiment-that-can-succeed/ Wed, 29 Jul 2026 12:00:00 GMT Most experiments fail before launch, because they were never large enough to detect the effect anyone hoped for. The fix costs ten minutes and happens before you write code. practice https://datanemics.com/blog/scheduled-posts/ https://datanemics.com/blog/scheduled-posts/ Tue, 28 Jul 2026 12:00:00 GMT The build refuses to publish a page whose date has not arrived, and a daily job does the rest. engineering https://datanemics.com/blog/pattern-slowly-changing-dimension-type-2/ https://datanemics.com/blog/pattern-slowly-changing-dimension-type-2/ Mon, 27 Jul 2026 12:00:00 GMT Keep every version of a row so "what was true in February" stays answerable after March changes it. warehousing modelling https://datanemics.com/blog/the-time-coverage-of-grid-energy-load/ https://datanemics.com/blog/the-time-coverage-of-grid-energy-load/ Sun, 26 Jul 2026 12:00:00 GMT 365 populated days across a 365-day span, and what that allows you to compute. engineering quality https://datanemics.com/blog/the-category-that-eats-the-chart-2026-07/ https://datanemics.com/blog/the-category-that-eats-the-chart-2026-07/ Sat, 25 Jul 2026 12:00:00 GMT 4 values with 44.3% concentrated in one of them, and what that does to every chart downstream. visualization practice https://datanemics.com/blog/a-running-total-that-does-not-lie-about-ties-2026-07/ https://datanemics.com/blog/a-running-total-that-does-not-lie-about-ties-2026-07/ Fri, 24 Jul 2026 12:00:00 GMT running total against a real schema, and the clause in it that is doing the work. sql https://datanemics.com/blog/the-total-came-out-8-2-too-high/ https://datanemics.com/blog/the-total-came-out-8-2-too-high/ Thu, 23 Jul 2026 12:00:00 GMT 8.2 rows per key on one table, and the totals that quietly inherit the multiplier. sql quality https://datanemics.com/blog/counting-rows-is-not-testing-grain-2026-07/ https://datanemics.com/blog/counting-rows-is-not-testing-grain-2026-07/ Wed, 22 Jul 2026 12:00:00 GMT 900 distinct combinations against 900 rows, and what that answers about the table's key. sql quality warehousing https://datanemics.com/blog/57-8-of-churned-at-is-missing/ https://datanemics.com/blog/57-8-of-churned-at-is-missing/ Tue, 21 Jul 2026 12:00:00 GMT 1,444 blanks in one column, and the one-line check that decides whether dropping them is free. quality statistics https://datanemics.com/blog/5-383-zeros-in-revenue-usd-and-what-they-mean/ https://datanemics.com/blog/5-383-zeros-in-revenue-usd-and-what-they-mean/ Mon, 20 Jul 2026 12:00:00 GMT 89.7% of one column is exactly zero. Whether that is a measurement or an absence changes every aggregate built on it. quality statistics https://datanemics.com/blog/before-you-clip-the-outliers-2026-07/ https://datanemics.com/blog/before-you-clip-the-outliers-2026-07/ Sun, 19 Jul 2026 12:00:00 GMT A max 1.4× the 99th percentile, and the three different things that could be. statistics quality https://datanemics.com/blog/the-average-distance-km-is-not-the-typical-one/ https://datanemics.com/blog/the-average-distance-km-is-not-the-typical-one/ Sat, 18 Jul 2026 12:00:00 GMT A 51.0% gap between mean and median on one column, and which of the two answers the question you were asked. statistics practice https://datanemics.com/blog/reading-reopened-before-trusting-it-in-support-tickets/ https://datanemics.com/blog/reading-reopened-before-trusting-it-in-support-tickets/ Fri, 17 Jul 2026 12:00:00 GMT 4,000 rows, 2 distinct values, and the one fact about reopened that changes how you query it. quality practice https://datanemics.com/blog/reading-3-columns-instead-of-12/ https://datanemics.com/blog/reading-3-columns-instead-of-12/ Thu, 16 Jul 2026 12:00:00 GMT Column pruning times partition pruning on a real schema, and the function call that quietly defeats both. performance warehousing https://datanemics.com/blog/gdp-per-capita-usd-by-region-a-105-spread/ https://datanemics.com/blog/gdp-per-capita-usd-by-region-a-105-spread/ Wed, 15 Jul 2026 12:00:00 GMT Real group means for one column across 5 segments, and what the pooled average conceals. statistics practice https://datanemics.com/blog/r-0-51-between-distance-km-and-tip-usd/ https://datanemics.com/blog/r-0-51-between-distance-km-and-tip-usd/ Tue, 14 Jul 2026 12:00:00 GMT A measured correlation of 0.51 between two columns, what its square says, and the diagnostic that costs one line. statistics https://datanemics.com/blog/correction-fan-out-join/ https://datanemics.com/blog/correction-fan-out-join/ Mon, 13 Jul 2026 12:00:00 GMT The page claimed more than it should have. What it says now, and where the pattern stops applying. quality practice https://datanemics.com/blog/my-experiment-came-back-flat-now-what/ https://datanemics.com/blog/my-experiment-came-back-flat-now-what/ Sun, 12 Jul 2026 12:00:00 GMT First, work out whether it was ever capable of detecting the effect you cared about. Compute the minimum detectable effect for the sample size you act experiments statistics https://datanemics.com/blog/how-scheduled-posts-work-here/ https://datanemics.com/blog/how-scheduled-posts-work-here/ Sat, 11 Jul 2026 12:00:00 GMT Posts carry a date in their front matter. Anything dated after the build date is written but not published: no page, no sitemap entry, no RSS item, no engineering production https://datanemics.com/blog/charting-baseline-score-by-arm/ https://datanemics.com/blog/charting-baseline-score-by-arm/ Fri, 10 Jul 2026 12:00:00 GMT Two facts about the columns decide the chart. Cardinality and skew, in that order. visualization https://datanemics.com/blog/the-interval-is-the-result-2026-07/ https://datanemics.com/blog/the-interval-is-the-result-2026-07/ Thu, 09 Jul 2026 12:00:00 GMT A point estimate of 7.1%, the interval around it, and what a tighter one would cost. statistics https://datanemics.com/blog/grid-energy-load-in-one-paragraph/ https://datanemics.com/blog/grid-energy-load-in-one-paragraph/ Wed, 08 Jul 2026 12:00:00 GMT A year of hourly electricity demand, renewable generation, temperature and wholesale price for one balancing area — including the hours when price goes negative.. quality practice https://datanemics.com/blog/what-data-explorer-will-not-do/ https://datanemics.com/blog/what-data-explorer-will-not-do/ Tue, 07 Jul 2026 12:00:00 GMT A fast table with per-column profiling: type inference, missing counts, distinct values, quantiles, and a sparkline distribution for every numeric column. visualization https://datanemics.com/blog/cutting-a-lesson-down-the-first-hour-with-an-unfamiliar-dataset/ https://datanemics.com/blog/cutting-a-lesson-down-the-first-hour-with-an-unfamiliar-dataset/ Mon, 06 Jul 2026 12:00:00 GMT A repeatable routine for finding out what you are actually holding, before you compute anything anyone will act on. practice https://datanemics.com/blog/saas-subscriptions-plan-4-values-94-0-in-the-top-three/ https://datanemics.com/blog/saas-subscriptions-plan-4-values-94-0-in-the-top-three/ Sun, 05 Jul 2026 12:00:00 GMT 4 values with 44.3% concentrated in one of them, and what that does to every chart downstream. visualization practice https://datanemics.com/blog/zero-is-not-a-small-number-2026-07/ https://datanemics.com/blog/zero-is-not-a-small-number-2026-07/ Sat, 04 Jul 2026 12:00:00 GMT 54.2% of one column is exactly zero. Whether that is a measurement or an absence changes every aggregate built on it. quality statistics https://datanemics.com/blog/date-spine-in-short-2026/ https://datanemics.com/blog/date-spine-in-short-2026/ Fri, 03 Jul 2026 12:00:00 GMT Join to a generated calendar so days with no activity appear as zero instead of vanishing. sql https://datanemics.com/blog/posted-on-runs-2023-01-01-to-2025-09-27/ https://datanemics.com/blog/posted-on-runs-2023-01-01-to-2025-09-27/ Thu, 02 Jul 2026 12:00:00 GMT 966 populated days across a 1,001-day span, and what that allows you to compute. engineering quality https://datanemics.com/blog/comparing-a-period-to-the-one-before-it-2026-07/ https://datanemics.com/blog/comparing-a-period-to-the-one-before-it-2026-07/ Wed, 01 Jul 2026 12:00:00 GMT period comparison against a real schema, and the clause in it that is doing the work. sql https://datanemics.com/blog/what-wind-mw-actually-contains-in-grid-energy-load/ https://datanemics.com/blog/what-wind-mw-actually-contains-in-grid-energy-load/ Tue, 30 Jun 2026 12:00:00 GMT 8,760 rows, 6,314 distinct values, and the one fact about wind_mw that changes how you query it. quality practice