Messy data
Raw data has missing values, wrong types, and the wrong shape. Learn to reshape, type, and merge it with d3.group, d3.rollup, and the array methods you already know.
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5 minutes readThe unglamorous 90%
Anyone who has worked with data for a while will tell you the same thing: data preparation takes most of your time. The chart you build at the end is the visible 10%. Cleaning, reshaping, and sanity-checking the data is the unglamorous 90%.
Fortunately, JavaScript and D3 ship with a strong toolkit for this kind of work. This lesson walks through the operations you will reach for over and over.
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