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我正在尝试绘制一个简单的图表（不能这么难！我之前已经成功使用过核心图！）。我有一些日期要绘制在 x 轴上。还有一些 y 轴上的小浮点值，比如 0.139503、0.139481 等。我必须绘制 5 个这样的值（我从后端获取）。对于 y 轴范围，我找到这些值中的最低值并将其设置为 y 轴范围的开始。并将majorIntervalLength 设置为(highestValue - LowestValue)/5，即（例如）0.007946。但是 y 轴间隔似乎固定为 1。所以，由于我的 y 轴值非常小（它们之间的差异在 0.01 左右），所有图都在 y=0.0 处绘制。这是代码片段：

-(void) initializeGraph {


    if ((self.graph == nil) || (self.graph == NULL)) {

        self.graphHostView = [(CPTGraphHostingView *) [CPTGraphHostingView alloc] initWithFrame:self.view.bounds];

        self.graph = [[CPTXYGraph alloc] initWithFrame:self.graphHostView.bounds];
    graph.paddingLeft   = 2.0;
    graph.paddingRight  = 2.0;
    graph.paddingTop    = 2.0;
    graph.paddingBottom = 2.0;
    graph.title = @"Graph Plot";

    // plotting style is set to line plots
    CPTMutableLineStyle *lineStyle = [CPTMutableLineStyle lineStyle];
    lineStyle.lineColor = [CPTColor blackColor];
    lineStyle.lineWidth = 2.0f;

    CPTXYAxisSet *axisSet = (CPTXYAxisSet *) self.graph.axisSet;
    axisSet.xAxis.majorTickLineStyle = lineStyle;
    axisSet.xAxis.majorTickLength = 7.0f;
    axisSet.xAxis.labelingPolicy = CPTAxisLabelingPolicyEqualDivisions;
    axisSet.yAxis.labelingPolicy = CPTAxisLabelingPolicyEqualDivisions;
    axisSet.xAxis.labelRotation = 90.0;
    CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *) self.graph.defaultPlotSpace;
    // Determine the lowest and highest values to be plotted in Y Axis)
    CGFloat yLow = 0.1;
    CGFloat yHigh = yLow;
    for (int i=0 ; i<self.dict.count ; i++) {
        MyCustomObject *myData = (MyCustomObject *) [dict objectForKey:
                                                           [self.arrayKeys objectAtIndex:i]];

        if (myData.mem < yLow) {
            yLow = myData.mem;
        }
        if (yHigh < myData.mem) {
            yHigh = myData.mem;
        }
    }
    plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0)
                                                  length:CPTDecimalFromFloat(5)];
    plotSpace.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(yLow)
                                                    length:CPTDecimalFromFloat(5)];

    // To determine the point where your graph starts
    //axisSet.yAxis.orthogonalCoordinateDecimal = CPTDecimalFromFloat(yLow);
    axisSet.yAxis.majorIntervalLength = CPTDecimalFromCGFloat((yHigh-yLow)/5.0);
    NSLog(@"Y axis interval : %f", (yHigh-yLow)/5.0);
    ...
}

-(NSNumber *) numberForPlot:(CPTPlot *)plot
                  field:(NSUInteger)fieldEnum
            recordIndex:(NSUInteger)index {
    if ( fieldEnum == CPTScatterPlotFieldY ) {
        return [NSNumber numberWithFloat:myData.mem];
    } else {
        return [NSNumber numberWithInt:index];
    }
}

为什么设置的 y 轴的 majorIntervalLength 不起作用？

4

2 回答 2

0

你在任何地方设置axisSet.yAxis.majorTickLength吗？我在上面的代码中没有看到它。

如果majorTickLength 为零，则刻度不会显示任何内容。

于 2013-05-03T14:30:44.113 回答
0

将 yRange 的长度（如 Erik Skroch 建议的那样）设置为 (yHigh-yLow) 有助于

于 2013-05-04T13:20:50.963 回答