如何仅显示“过去24小时"从“最后72小时"开始JFreeChart时间序列 [英] How to display only "last 24 hours" from a "last 72 hours" JFreeChart TimeSeries

问题描述

我编写了这两行代码以使用XYDataset创建图表:

I wrote these 2 lines of code to create a chart using an XYDataset:

final XYDataset dataset = new TimeSeriesCollection(myInfo.getSeries());
JFreeChart timechart = ChartFactory.createTimeSeriesChart(myInfo.getName()
    + " CPU (last 72h)", "", "CPU %", dataset, false, false, false);

这些行创建了一个很好的过去72小时"图表:

These lines created this nice "last 72h" chart:

这是我添加信息以构建此图表的方式(这段代码可以多次运行):

This is how I added the information to build this chart (this piece of code can run multiple times):

SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd H:mm:ss");
Date date = simpleDateFormat.parse(dateAsStringToParse);
Second second = new Second(date);
myInfo.getSeries().addOrUpdate(second, maxValue); // maxValue is an Integer

我想要一个(看似)简单的更改-仅将此更改剪切"到最后24小时.我的意思是只在图表中看到最近的24小时，就像这样(图片中是我使用相同技术制作的另一张图表，但是信息仅在最近的24小时内存在):

I want a (seemingly) simple alteration—to "cut" this only to the last 24 hours. I mean to see only the most "recent" 24 hours in the graph, like so (in the picture is a different chart I made using the same technique, but the information exists only for the last 24hrs):

我浏览了API，找不到合适的答案，因为我认为这应该有一些聪明而简单的解决方案.

I have looked through the API and could not find an appropriate answer, as I believe this should have some clever but simple solution.

推荐答案

而不是像建议的那样丢弃旧数据， SlidingCategoryDataset 提供了此功能CategoryDataset的功能，XYDataset没有内置的解决方案. SlidingXYDataset(在此处中看到)，也许是另一种选择.在下面说明的SliderDemo2的变体中，我将三天的数据添加到具有一日窗口的单个系列中.我保留了滑块，以便于查看较早的值.

Instead of discarding old data, as suggested here, it looks like you want to display a contiguous subset of the data, as if looking through a window. While SlidingCategoryDataset provides this feature for a CategoryDataset, there is no built-in solution for an XYDataset. SlidingXYDataset, seen here, maybe an alternative. In the variation of SliderDemo2 illustrated below, I've added three days of data to a single series with a one day window. I've retained the slider for easy review of earlier values.

static final int COUNT = 3 * 24 * 60;
public static final int WINDOW = 24 * 60;
public static final int FIRST = 2 * 24 * 60;
…
this.slider.setValue(FIRST);

顺便说一句，请注意，自提交补丁以来，有些类已经移动:

As an aside, note that some classes have moved since the patch was submitted:

import org.jfree.ui.ApplicationFrame;
import org.jfree.ui.RefineryUtilities;

我不能只是使用setMaximumItemAge()吗?

不是孤立的； addOrUpdate()，等，在通知侦听器之前先调用removeAgedItems(false).

Not in isolation; addOrUpdate(), et al., calls removeAgedItems(false) before notifying listeners.

我正在使用Second.

Second数据的三天时间表示setMaximumItemAge(3 * 24 * 60 * 60).

Threes days of Second data, e.g., would imply setMaximumItemAge(3 * 24 * 60 * 60).

由于我将图表另存为JPEG，因此可能无法使用滑动窗口.

A sliding window might not be available to me since I am saving the chart as a JPEG.

您可以将所需的firstItemIndex作为参数传递给SlidingXYDataset构造函数；您可以稍后根据需要通过setFirstItemIndex()更新索引.

You can pass the desired firstItemIndex as a parameter to the SlidingXYDataset constructor; you can update the index later via setFirstItemIndex() if needed.

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