Question

我试图绘制一个简单的图形（不能太难！我以前成功使用过核心图！）。我有一些日期要在x轴上绘制。并且y轴上有一些小的浮点值，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轴范围的起点。并将majorIntervalLength设置为（highestValue - LowestValue）/ 5，即（例如）0.007946。但是y轴间隔似乎固定在1的间隔。因此，由于我的y轴值非常小（它们之间的差值大约为0.01），所以所有绘图都是在y = 0.0时绘制的。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];
    }
}

为什么设置不起作用的y轴的majorIntervalLength？

Answer 1

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，则不会显示任何内容。

Answer 2

将范围长度（如Erik Skroch所建议）设置为（tHigh-yelLow）帮助

核心情节majorIntervalLength：无法使其工作

2 个答案: