January Wheat Selloff Hit 9.6 percent Peak-to-Trough in Three Weeks , Futures Recovered Through February as Supply Concerns Eased Figure 49.1 , January Wheat Selloff and Recovery

An OHLC chart encodes four price dimensions per time period with a single symbol. A vertical line spans the session's high and low , the full intraday range. Two horizontal ticks branch off this line: one on the left at the opening price, one on the right at the closing price.

The candlestick chart encodes the same four values but uses a filled rectangle (the "body") for the open-to-close range, with thin wicks extending to the high and low. The body's fill distinguishes bullish from bearish. For sparse time series (weekly, monthly data, or fewer than ~20 sessions), candlestick bodies are immediately legible. For dense series , 40+ daily sessions , the filled bodies begin to occlude each other, and the chart reads as a mass of colored blocks rather than distinct symbols.

A line chart of closing prices would show the January peak and trough clearly, but would erase all intraday information. The session of Jan 18 , in which the price opened at 608.6 and fell 16 cents to close at 599.4, with an intraday low of 596.8 , is analytically significant for food security analysis. The low of 596.8 means that at some point during that session, wheat was accessible at a price not seen since mid-December.

Unlike bar charts, the OHLC y-axis does not start at zero. For bar charts, a zero baseline is mandatory because bar length encodes absolute magnitude , a bar twice as long should represent twice the value, which only holds when the baseline is zero. The OHLC chart encodes change, not absolute magnitude. The viewer's question is "how much did the price move?" not "how large is the price?" A wheat price of zero has no meaning , the commodity would not exist.

framework , FT Visual Vocabulary The FT Visual Vocabulary places OHLC charts in the Change Over Time category alongside line charts and area charts, with an additional Ranges quality for the high-low dimension. Its guidance on axis truncation for time-series charts: truncation is acceptable when the analyst's goal is to show change rather than absolute quantity. The OHLC chart's entire purpose is change , this is the one chart type where a zero baseline would be actively misleading.

Paste this into Claude Code to generate a working version of this chart, plus its data file. The result will not be a perfect replica , the goal is that the reader can run the prompt, get a chart of this type, and read its source. Generate a complete, self-contained ohlc chart in D3 v7. Two files:

The ideas in this chapter didn't appear from nowhere. Ralph Nelson Elliott developed Elliott Wave Theory in the 1930s , a system of reading OHLC price charts as nested fractal patterns of impulse waves and corrections. The theory is contested but the chart-reading discipline it produced is widespread. Ralph Nelson Elliott, circa 1935. AI-generated portrait based on a public domain photograph (Wikimedia Commons).

The ideas in this chapter didn't appear from nowhere. Ralph Nelson Elliott developed Elliott Wave Theory in the 1930s , a system of reading OHLC price charts as nested fractal patterns of impulse waves and corrections. The theory is contested but the chart-reading discipline it produced is widespread. Ralph Nelson Elliott, circa 1935. AI-generated portrait based on a public domain photograph (Wikimedia Commons).