使用 CorePlot 制作图表

Core Plot 提供了 podspec，因此你可以使用 cocoapods 作为你的库管理器，这将使安装和更新变得更加简单

在你的系统上安装 cocoapods

在项目目录中，通过在项目目录中键入 pod init，将一个文本文件添加到名为 Podfile 的项目中

在 Podfile 中添加行 pod’CorePlot’，’〜> 1.6'

在终端中，cd 到项目目录并运行 pod install

Cocoapods 将生成一个 xcworkspace 文件，你应该用它来启动你的项目（.xcodeproj 文件将不包含 pod 库）

打开 CocoaPods 生成的 .xcworkspace

在 ViewController.h 文件中

#import <CorePlot/ios/CorePlot.h>
//#import "CorePlot-CocoaTouch.h" or the above import statement
@interface ViewController : UIViewController<CPTPlotDataSource>

在 ViewController.m 文件中

-(void)loadView
{
    [super loadView];
    // We need a hostview, you can create one in IB (and create an outlet) or just do this:
    CPTGraphHostingView* hostView = [[CPTGraphHostingView alloc] initWithFrame:CGRectMake(10, 40, 300, 400)];
    hostView.backgroundColor=[UIColor whiteColor];
    self.view.backgroundColor=[UIColor blackColor];
    [self.view addSubview: hostView];
    // Create a CPTGraph object and add to hostView
    CPTGraph* graph = [[CPTXYGraph alloc] initWithFrame:CGRectMake(10, 40, 300, 400)];
    hostView.hostedGraph = graph;
    // Get the (default) plotspace from the graph so we can set its x/y ranges
    CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *) graph.defaultPlotSpace;
    // Note that these CPTPlotRange are defined by START and LENGTH (not START and END) !!
    [plotSpace setYRange: [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat( 0 ) length:CPTDecimalFromFloat( 20 )]];
    [plotSpace setXRange: [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat( -4 ) length:CPTDecimalFromFloat( 8 )]];
    // Create the plot (we do not define actual x/y values yet, these will be supplied by the datasource...)
    CPTScatterPlot* plot = [[CPTScatterPlot alloc] initWithFrame:CGRectZero];
    // Let's keep it simple and let this class act as datasource (therefore we implemtn <CPTPlotDataSource>)
    plot.dataSource = self;
    // Finally, add the created plot to the default plot space of the CPTGraph object we created before
    [graph addPlot:plot toPlotSpace:graph.defaultPlotSpace];
}
// This method is here because this class also functions as datasource for our graph
// Therefore this class implements the CPTPlotDataSource protocol
-(NSUInteger)numberOfRecordsForPlot:(CPTPlot *)plotnumberOfRecords
{
        return 9; // Our sample graph contains 9 'points'
}
// This method is here because this class also functions as datasource for our graph
// Therefore this class implements the CPTPlotDataSource protocol
-(NSNumber *)numberForPlot:(CPTPlot *)plot field:(NSUInteger)fieldEnum recordIndex:(NSUInteger)index
{
    // We need to provide an X or Y (this method will be called for each) value for every index
    int x = index - 4;
    // This method is actually called twice per point in the plot, one for the X and one for the Y value
    if(fieldEnum == CPTScatterPlotFieldX)
    {
    // Return x value, which will, depending on index, be between -4 to 4
    return [NSNumber numberWithInt: x];
    } else
    {
    // Return y value, for this example we'll be plotting y = x * x
        return [NSNumber numberWithInt: x * x];
    }
}

生成的输出如下：