Understanding Core Plot and Creating a Stock Volume Chart Using Core Plot

Understanding Core Plot and Creating a Stock Volume Chart

Introduction

Core Plot is a powerful, open-source plotting library for Objective-C, used primarily in iOS development. It allows developers to create high-quality charts and graphs with ease. In this article, we’ll explore how to implement a stock volume chart using Core Plot on iPhone.

What is Core Plot?

Core Plot is a free, open-source plotting library developed by Apple. It’s part of the Xcode project template, making it easy for developers to incorporate into their iOS projects. Core Plot provides an extensive set of tools and features to create professional-grade charts and graphs, including line plots, scatter plots, histograms, and more.

Choosing the Right Chart Type

When it comes to creating a stock volume chart, you’ll want to use a type of chart that can effectively display both price data and volume information. There are several types of charts you could consider:

Line plot: This is suitable for displaying price trends over time.
Bar chart: This can be used to display volume data on the y-axis.
Combination chart: This can overlay multiple series (price, volume) onto a single chart.

Using Core Plot to Create a Stock Volume Chart

To create a stock volume chart using Core Plot, we’ll need to follow these steps:

Step 1: Importing Core Plot

First, make sure you have the Core Plot framework imported in your Xcode project. To do this, navigate to xcassets > AppIcon > CorePlot, and select the CorePlot.xcassets file.

Step 2: Setting Up the Chart Data

Create a new Objective-C class that will hold your chart data. In this example, we’ll use a simple StockChartData class to store our price and volume arrays:

#import <Foundation/Foundation.h>
#import <CorePlot/CorePlot.h>

@interface StockChartData : NSObject

@property (nonatomic) NSArray \*price;
@property (nonatomic) NSArray \*volume;

@end

Create an initializer method for the StockChartData class that initializes the price and volume arrays:

- (instancetype)init {
    self = [super init];
    if (self) {
        // Initialize price and volume arrays with sample data
        self.price = @[@50.0, @60.0, @55.0, @65.0, @70.0, @75.0, @80.0, @85.0, @90.0, @95.0];
        self.volume = @[@10000.0, @12000.0, @11000.0, @14000.0, @16000.0, @17000.0, @18000.0, @19000.0, @20000.0, @21000.0];
    }
    return self;
}

Step 3: Creating the Chart

Create a new method for your view controller that will create and display the chart:

- (void)createStockVolumeChart {
    // Create a new chart view
    CPXYPlot *plot = [[CPXYPlot alloc] init];
    
    // Set up plot space dimensions
    [plot setFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
    [plot setOuterFrameRadius:10.0];
    
    // Create a line plot for price data
    CPLineSeries *priceSeries = [[CPLineSeries alloc] init];
    priceSeries.lineColor = [CPTColor redColor];
    priceSeries.dataDetector = CPTDataDetectorNone;
    
    // Create a line plot for volume data
    CPLineSeries *volumeSeries = [[CPLineSeries alloc] init];
    volumeSeries.lineColor = [CPTColor greenColor];
    volumeSeries.dataDetector = CPTDataDetectorNone;
    
    // Add series to the plot
    [plot addSeries:priceSeries];
    [plot addSeries:volumeSeries];
    
    // Set up chart style
    CPXYAxis *xAxis = [[CPXYAxis alloc] init];
    xAxis.labelFont = [NSFont systemFontOfSize:12.0];
    xAxis.tickLabelFormatter = [[CPTMutableTextFormatter alloc] initWithColor:CPTColor grayColor];
    [plot setXAxis:xAxis];
    
    CPXYAxis *yAxis = [[CPXYAxis alloc] init];
    yAxis.labelFont = [NSFont systemFontOfSize:12.0];
    yAxis.tickLabelFormatter = [[CPTMutableTextFormatter alloc] initWithColor:CPTColor grayColor];
    [plot setYAxis:yAxis];
    
    // Set plot background color
    CPXYPlotSpace *plotSpace = [[CPXYPlotSpace alloc] init];
    [plotSpace setLimitLineWidth:5.0];
    [plotSpace setPlotToView:self.view];
    [plotSpace setLimits:CGRectMake(0, 0, 100, 300)];
    
    // Set up plot with chart data
    CPXYPlot *result = [[CPXYPlot alloc] initWithFrame:self.view.bounds];
    result.plotSpace = plotSpace;
    result.preset = CPPlotPresetLineChartWithNoDataColor;

    [self view addSubview:([result subviews][0])];

    // Update chart with data
    StockChartData *chartData = [[StockChartData alloc] init];
    priceSeries.data = chartData.price;
    volumeSeries.data = chartData.volume;

    CPXYPlotView *plotView = [[CPXYPlotView alloc] initWithFrame:self.view.bounds];
    plotView.plot = plot;
    [self.view addSubview:plotView];
}

Step 4: Updating the Chart with New Data

Create a new method to update your chart data:

- (void)updateChart {
    // Update chart series with sample data
    CPXYPlot *chart = [[CPXYPlot alloc] init];
    CPXYPlotSpace *plotSpace = [[CPXYPlotSpace alloc] init];
    [plotSpace setLimitLineWidth:5.0];
    [plotSpace setPlotToView:self.view];
    [plotSpace setLimits:CGRectMake(0, 0, 100, 300)];
    
    CPXYAxis *xAxis = [[CPXYAxis alloc] init];
    xAxis.labelFont = [NSFont systemFontOfSize:12.0];
    xAxis.tickLabelFormatter = [[CPTMutableTextFormatter alloc] initWithColor:CPTColor grayColor];
    [chart setXAxis:xAxis];
    
    CPXYAxis *yAxis = [[CPXYAxis alloc] init];
    yAxis.labelFont = [NSFont systemFontOfSize:12.0];
    yAxis.tickLabelFormatter = [[CPTMutableTextFormatter alloc] initWithColor:CPTColor grayColor];
    [chart setYAxis:yAxis];

    CPXYLineSeries *lineSeries = [[CPXYLineSeries alloc] init];
    lineSeries.lineColor = [CPTColor redColor];
    lineSeries.dataDetector = CPTDataDetectorNone;
    
    CPXYLineSeries *volumeSeries = [[CPXYLineSeries alloc] init];
    volumeSeries.lineColor = [CPTColor greenColor];
    volumeSeries.dataDetector = CPTDataDetectorNone;

    CPXYPlot *result = [[CPXYPlot alloc] initWithFrame:self.view.bounds];
    result.plotSpace = plotSpace;
    result.preset = CPPlotPresetLineChartWithNoDataColor;
    [chart addSeries:lineSeries];
    [chart addSeries:volumeSeries];

    StockChartData *chartData = [[StockChartData alloc] init];
    lineSeries.data = chartData.price;
    volumeSeries.data = chartData.volume;

    CPXYPlotView *plotView = [[CPXYPlotView alloc] initWithFrame:self.view.bounds];
    plotView.plot = chart;
    [self.view addSubview:plotView];

}

Step 5: Display the Chart

Finally, display your chart:

- (void)viewDidLoad {
    [super viewDidLoad];
    self.createStockVolumeChart;
}

Conclusion

This guide has walked you through the process of creating a stock volume chart with multiple lines using Core Plot. By following these steps, you can create your own chart and display it in your app.

Here’s an example of what this might look like at runtime:

[Insert image of a line chart displaying two lines]

This is just a basic example and there are many ways to customize the appearance and behavior of the chart.

Note: This is just one way to create a stock volume chart with multiple lines using Core Plot. There are other ways to do it, and you can experiment with different styles and customization options to find what works best for your app.

Getting Started

To get started with this example, make sure you have the following frameworks installed:

CorePlot.framework

Also, be sure to import the necessary files in your view controller file.

Last modified on 2024-09-02