Bdtjtk

I'd using JavaFX to draw barcharts which represents a sound power. The range of my values are from -60 to +3 dbBF (decibel full scale).

When JavaFX draw the "bars", the baseline is always set to 0 so, my bars are drawn from 0 to +X (above the zero line) or from 0 to -X (below the zero line).

My aim is to get a bar from -60 to -X. Is there a way to set the baseline origin to -60 ? I looked for tips on google and tried few things but nothing worked.

Thank you for your answers.

I'm not aware of a way to change the baseline of a JavaFX chart. However, you can make it look like it's starting from -60. The ValueAxis (and by extension, NumberAxis) class has a property for formatting the tick labels: tickLabelFormatter. You can supply your own StringFormatter that makes the labels "off by 60". Here's an example:

import javafx.application.Application;

import javafx.collections.FXCollections;

import javafx.scene.Scene;

import javafx.scene.chart.BarChart;

import javafx.scene.chart.CategoryAxis;

import javafx.scene.chart.NumberAxis;

import javafx.scene.chart.XYChart.Data;

import javafx.scene.chart.XYChart.Series;

import javafx.stage.Stage;

import javafx.util.StringConverter;



public class App extends Application {



  @Override

  public void start(Stage primaryStage) throws Exception {

    var scene = new Scene(createChart() 600, 400);

    primaryStage.setScene(scene);

    primaryStage.setTitle("SO-53959031");

    primaryStage.show();

  }



  @SuppressWarnings("unchecked")

  private Series<String, Number> createData() {

    return new Series<>(FXCollections.observableArrayList(

        new Data<>("Test #0", 40),

        new Data<>("Test #1", 20),

        new Data<>("Test #2", 63),

        new Data<>("Test #3", 50),

        new Data<>("Test #4", 30)

    ));

  }



  private BarChart<String, Number> createChart() {

    var yAxis = new NumberAxis("dbBF", 0, 63, 1);

    yAxis.setTickLabelFormatter(new StringConverter<>() {

      @Override

      public String toString(Number object) {

        return Double.toString(object.doubleValue() - 60);

      }



      @Override

      public Number fromString(String string) {

        return Double.valueOf(string) + 60;

      }

    });



    var chart = new BarChart<>(new CategoryAxis(), yAxis);

    chart.getData().add(createData());

    chart.setLegendVisible(false);

    return chart;

  }



}

There's a caveat: You have to translate your data to be zero-based. This only has to be done for the chart's data. In other words, your model can keep the data between -60 and 3 but it has to be translated to be in the range 0 to 63 for the chart.

Screenshot of example: