coco
78 lines
2.8 KiB
Markdown
78 lines
2.8 KiB
Markdown
# Candlestick Charts
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Candlestick charts are a special kind of `XYPlot` usually used for rendering financial information.
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Each "candlestick" is composed of 4 values: open, close, high and low.
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Androidplot's implementation of candlestick charts uses four separate `XYSeries` instances to represent
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the candlestick values; each series corresponds to one of the four values that composes each "candlestick".
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For example:
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```java
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Number[] highVals = new Number[] {12, 10, 15, 8, 7};
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Number[] lowVals = new Number[] {3, 1, 5, 0, 2};
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Number[] openVals = new Number[] {5, 2, 7, 5, 3};
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Number[] closeVals = new Number[] {7, 9, 6, 0, 4};
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```
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Using the values above, the first candlestick model would be `{high=12, low=3, open=5, close=7}`,
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the second would be `{high=10, low=1, open=2, close=7}` and so on.
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There are a few constraints that must be satisfied before we can create XYSeries from the data above and add them to Androidplot:
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* Each series must be of the same size.
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* Each series must have the same x(i); getX(i) must return the same value for each series.
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* There must be exactly four series, added in the precise order: high, low, open, close.
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* The series data must make sense; each candlestick's high must be equal to or greater than all other
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values in the candlestick, and each candlestick's low must be less than or equal to all other values.
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* Each candlestick series belonging to the same candlestick chart must use the same `CandlestickFormatter`
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instance when being added to the XYPlot.
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While it's possible to satisfy these constraints by creating each of the four `XYSeries` required by a
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candlestick chart, adding them in order using the same formatter, many projects will find it simpler
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to interact with the data as though it were a single series of candlestick values. To makr this easier,
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two convenience classes: `CandlestickSeries` and `CandlestickMaker`. Here's how they are used together to add a candlestick chart to an `XYPlot`:
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```java
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CandlestickSeries candlestickSeries = new CandlestickSeries(
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new CandlestickSeries.Item(1, 10, 2, 9),
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new CandlestickSeries.Item(4, 18, 6, 5),
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new CandlestickSeries.Item(3, 11, 5, 10),
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new CandlestickSeries.Item(2, 17, 2, 15),
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new CandlestickSeries.Item(6, 11, 11, 7),
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new CandlestickSeries.Item(8, 16, 10, 15));
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CandlestickFormatter formatter = new CandlestickFormatter();
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// add the candlestick series data to the plot:
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CandlestickMaker.make(plot, formatter, candlestickSeries);
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```
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It's necessary to use `CandlestickMaker` to add the `CandlestickSeries` (via "make") to the
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`XYPlot` as `CandlestickSeries` does not and cannot implement the `XYSeries` interface.
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[A full source example is available here](../demoapp/src/main/java/com/androidplot/demos/CandlestickChartActivity.java).
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