This issue might be related to issue RT-30876. I add two series to a line chart. I then remove one of the series and change the y-data values. When I add the series back to the chart, the chart does not display the changed data values; it displays the data as it was when it was removed from the chart.

Below is a small application that demonstrates the problem. When the series is added back to the plot, I print the changed values to the console so you can see the values are changed but that change is not reflected on the plot.

This problem also occurs in Java 8 / JavaFX 8 (specifically 8.0.0-ea-b92 [30 May 2013]).

package com.scenaria.sandbox;

import javafx.application.Application;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.scene.chart.XYChart.Series;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class ChangeDataTest extends Application {
    
    @Override
    public void start(Stage stage) {
        stage.setTitle("Line Chart Sample");
        
        final NumberAxis xAxis = new NumberAxis();
        final NumberAxis yAxis = new NumberAxis();
        xAxis.setLabel("Month Number");
        
        final LineChart<Number,Number> lineChart =
                new LineChart<Number,Number>(xAxis,yAxis);
        lineChart.setTitle("Stock Monitoring, 2010");
        
        XYChart.Series series1 = new XYChart.Series();
        series1.setName("Series 1");
        series1.getData().add(new XYChart.Data(1, 23));
        series1.getData().add(new XYChart.Data(3, 15));
        series1.getData().add(new XYChart.Data(5, 34));
        series1.getData().add(new XYChart.Data(7, 22));
        series1.getData().add(new XYChart.Data(9, 43));
        series1.getData().add(new XYChart.Data(11, 29));
        
        final XYChart.Series series2 = new XYChart.Series();
        series2.setName("Series 2");
        series2.getData().add(new XYChart.Data(1, 10));
        series2.getData().add(new XYChart.Data(3, 11));
        series2.getData().add(new XYChart.Data(5, 28));
        series2.getData().add(new XYChart.Data(7, 18));
        series2.getData().add(new XYChart.Data(9, 35));
        series2.getData().add(new XYChart.Data(11, 22));
        
        BorderPane bdrPane = new BorderPane();
        bdrPane.setCenter(lineChart);
        
        Button rmSeries2Btn = new Button();
        rmSeries2Btn.setText("Remove Series 2");
        rmSeries2Btn.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent t) {
                ObservableList<Series<Number, Number>> data = lineChart.getData();
                Series<Number, Number> removedSeries = data.remove(1);
            }
        });
        
        Button changeSeriesBtn = new Button();
        changeSeriesBtn.setText("Change Series");
        changeSeriesBtn.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent t) {
                ObservableList<XYChart.Data<Number, Number>> data = series2.getData();
                for (XYChart.Data<Number, Number> dataPoint : data) {
                    double newValue = dataPoint.getYValue().doubleValue() * 1.25;
                    dataPoint.setYValue(newValue);
                }
            }
        });
        
        Button addSeriesBackBtn = new Button();
        addSeriesBackBtn.setText("Add Series Back");
        addSeriesBackBtn.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent t) {
                System.out.println("Series 2 Data:");
                ObservableList<XYChart.Data<Number, Number>> data = series2.getData();
                for (XYChart.Data<Number, Number> dataPoint : data) {
                    double xValue = dataPoint.getXValue().doubleValue();
                    double yValue = dataPoint.getYValue().doubleValue();
                    System.out.println(" (" + xValue + ", " + yValue +")");
                }
                
                lineChart.getData().add(series2);
            }
        });
        
        HBox buttonHBox = new HBox();
        buttonHBox.getChildren().addAll(rmSeries2Btn, changeSeriesBtn, addSeriesBackBtn);
        bdrPane.setBottom(buttonHBox);
        
        Scene scene = new Scene(bdrPane,800,600);
        
        lineChart.getData().add(series1);
        lineChart.getData().add(series2);
       
        stage.setScene(scene);
        stage.show();
        
        System.out.println("JavaFX version: " + System.getProperties().get("javafx.runtime.version"));
        System.out.println("Java version: " + System.getProperties().get("java.version"));
    }
 
    public static void main(String[] args) {
        launch(args);
    }
    
}