Histogram Maker

How the Histogram Maker works

Histogram maker: getting a good result

Data. Paste a single column of numbers with a header, or just the numbers; the first column that contains numbers is used and anything non-numeric in it is skipped. Unlike the bar chart, the histogram takes raw observations rather than already-counted totals: thirty heights, two hundred response times, a year of daily temperatures. The page does the counting.

Bins. Auto picks a bin count from the number of values using Sturges' rule, which gives five or six bins for thirty values and around eleven for a thousand, then rounds the edges to tidy numbers so the axis reads 160, 165, 170 rather than 161.3, 166.1. Choose a fixed count to override it. Too few bins hide the shape; too many break it into noise. Try a couple of settings and use the one where the shape is stable, and say in the caption which you used, because the same data can look unimodal at eight bins and bimodal at twenty.

Count or percent. Count shows the number of values in each bin, which is the plain frequency distribution. Percent shows each bin's share of the whole, which is the right axis when comparing histograms of different sample sizes side by side. Bar labels print the value above each bar in whichever unit is selected.

Mean and median. The dashed lines mark the average and the middle value. When the two sit together the distribution is roughly symmetric; when the mean is pulled away from the median towards one tail, the data is skewed that way. The stats below the chart give both, with the standard deviation and the minimum and maximum, so the chart and its summary numbers come from one place.

Export. Download SVG gives a vector file for reports, Download PNG renders it at 1×, 2× or 3× the preview width on white, and Copy SVG puts the markup on the clipboard. The binning and the statistics are computed in the browser and the numbers are never uploaded.

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