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JMSL Chart Programmer's Guide
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Charting 2D Types >> Error Bar Plot |
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Error Bar Plot
Error bars are used to indicate the estimated error in a measurement. Errors bars indicate the uncertainty in the x and/or y values.
Vertical Error Bars
The most common error bar plot is one in which the errors are in the y-values. This example shows such an error bar plot. Note that the values of the low and high arguments are absolute y values, not relative or percentage values.
(Download Code)
import com.imsl.chart.*; import java.awt.Color; import com.imsl.stat.Random; public class SampleErrorBar extends JFrameChart { public SampleErrorBar() { Random r = new Random(123457); Chart chart = getChart(); AxisXY axis = new AxisXY(chart); // Generate a random data set, with random errors int n = 20; double x[] = new double[n]; double y[] = new double[n]; double low[] = new double[n]; double high[] = new double[n]; for (int k = 0; k < n; k++) { x[k] = k + 1; y[k] = r.nextDouble(); low[k] = y[k] - 0.25*r.nextDouble(); high[k] = y[k] + 0.25*r.nextDouble(); } ErrorBar data = new ErrorBar(axis, x, y, low, high); data.setDataType(data.DATA_TYPE_ERROR_Y | data.DATA_TYPE_MARKER); data.setMarkerType(Data.MARKER_TYPE_FILLED_CIRCLE); data.setMarkerColor(Color.red); } public static void main(String argv[]) { new SampleErrorBar().setVisible(true); } }
Horizontal Error Bars
It is also possible to have horizontal error bars, indicating errors in x, as shown in this example.
(Download Code)
import com.imsl.chart.*; import java.awt.Color; import com.imsl.stat.Random; public class SampleHorizontalErrorBar extends JFrameChart { public SampleHorizontalErrorBar() { Random r = new Random(123457); Chart chart = getChart(); AxisXY axis = new AxisXY(chart); // Generate a random data set, with random errors in x int n = 20; double x[] = new double[n]; double y[] = new double[n]; double low[] = new double[n]; double high[] = new double[n]; for (int k = 0; k < n; k++) { x[k] = k; y[k] = r.nextDouble(); low[k] = x[k] - 5.*r.nextDouble(); high[k] = x[k] + 5.*r.nextDouble(); } ErrorBar data = new ErrorBar(axis, x, y, low, high); data.setDataType(data.DATA_TYPE_ERROR_X | data.DATA_TYPE_MARKER); data.setMarkerType(Data.MARKER_TYPE_FILLED_CIRCLE); data.setMarkerColor("red"); } public static void main(String argv[]) { new SampleHorizontalErrorBar().setVisible(true); } }
Mixed Error Bars
To show errors in both x and y, it is necessary to create both vertical and horizontal error bar objects. This example shows such a chart.
import com.imsl.chart.*; import java.awt.Color; import com.imsl.stat.Random; public class SampleMixedErrorBar extends JFrameChart { public SampleMixedErrorBar() { Random r = new Random(123457); Chart chart = getChart(); AxisXY axis = new AxisXY(chart); // Generate a random data set, with random errors in x int n = 20; double x[] = new double[n]; double y[] = new double[n]; double xlow[] = new double[n]; double xhigh[] = new double[n]; double ylow[] = new double[n]; double yhigh[] = new double[n]; for (int k = 0; k < n; k++) { x[k] = k; y[k] = r.nextDouble(); xlow[k] = x[k] - r.nextDouble(); xhigh[k] = x[k] + r.nextDouble(); ylow[k] = y[k] - 0.25*r.nextDouble(); yhigh[k] = y[k] + 0.25*r.nextDouble(); } ErrorBar dataY = new ErrorBar(axis, x, y, ylow, yhigh); dataY.setDataType(dataY.DATA_TYPE_ERROR_Y | dataY.DATA_TYPE_MARKER); dataY.setMarkerType(Data.MARKER_TYPE_FILLED_CIRCLE); dataY.setMarkerColor("red"); ErrorBar dataX = new ErrorBar(axis, x, y, xlow, xhigh); dataX.setDataType(dataY.DATA_TYPE_ERROR_X); dataX.setMarkerColor("red"); } public static void main(String argv[]) { new SampleMixedErrorBar().setVisible(true); } }
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