目标-C:获取 NSMutableArray 中的最小值/最大值
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23-09-2019 - |
题
我想获取 NSMutableArray 的最大值和最小值,以便我可以基于这些最大值和最小值创建核心图绘图空间和图表。
我的代码如下:
NSMutableArray *contentArray = [NSMutableArray arrayWithCapacity:100];
NSUInteger i;
for (i=0; i<60; i++){
id x = [NSNumber numberWithFloat:i*0.05];
id y = [NSNumber numberWithFloat:1.2*rand()/(float)RAND_Max + 0.6];
[contentArray addObject:[NSMutableDictionary dictionaryWithObjectsAndKeys:x, @"x", y, @"y", nil]];
}
self.dataForPlot = contentArray;
CPXYPlotSpace *plotSpace = (CPXYPlotSpace *)graph.defaultPlotSpace;
plotSpace.xRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat() length:CPDecimalFromFloat()];
plotSpace.yRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat() length:CPDecimalFromFloat()];
如果我希望图形仅跨越 contentArray 中指定的空间,我该如何填写 xRange 和 yRange 分配的空白?
没有正确的解决方案
其他提示
在这种情况下,您应该使用 -[CPPlotSpace scaleToFitPlots:]
. 。有关数组值的更一般计算,请继续阅读...
这是键值编码和相关联的理想用途 数组运算符. 。在你的例子中,
float maxX = [[contentArray valueForKeyPath:@"@max.x"] floatValue];
float minY = [[contentArray valueForKeyPath:@"@min.x"] floatValue];
float maxY = [[contentArray valueForKeyPath:@"@max.y"] floatValue];
float minY = [[contentArray valueForKeyPath:@"@min.y"] floatValue];
数组运算符调用 valueForKeyPath:
于 contentArray
它给出了一个通过调用相同的方法构建的数组 valueForKeyPath:
在数组的每个成员上,键路径位于数组运算符右侧(即 @min
和 @max
)。然后,原始调用将给定的运算符应用于结果数组。您可以轻松地定义一个类别 NSArray
给你一个最小/最大值的结构:
typedef struct {
float minX;
float minY;
float maxX;
float maxY;
} ArrayValueSpace;
@implementation NSArray (PlotSpaceAdditions)
- (ArrayValueSpace)psa_arrayValueSpace {
ArrayValueSpace result;
result.maxX = [[contentArray valueForKeyPath:@"@max.x"] floatValue];
result.minX = [[contentArray valueForKeyPath:@"@min.x"] floatValue];
result.maxY = [[contentArray valueForKeyPath:@"@max.y"] floatValue];
result.minY = [[contentArray valueForKeyPath:@"@min.y"] floatValue];
return result;
}
您可以找到最大值和最小值时填写,但在你的代码段使用时它只是工作。如果你想要更多的东西通用的,你应该简单地浏览清单,并寻找它。
// contentArray already defined
int maxX = 0, minX = 1000, maxY = 0, minY = 1000;
for (int i = 0; i < [contentArray count]; ++1)
{
int curX = [[[contentArray objectForKey:@"x"] objectAtIndex:i] integerValue];
int curY = [[[contentArray objectForKey:@"y"] objectAtIndex:i] integerValue];
if (curX < minX)
minX = curX;
else if (curX > maxX)
maxX = curX;
if (curY < minY)
minY = curY;
else if (curY > maxY)
maxY = curY;
}
您可以通过阵列使用快速枚举。
NSUInteger maxX = 0;
NSUInteger minX = 0xFFFFFFFF; //(for 32 bit)
NSUInteger maxY = 0;
NSUInteger minY = 0xFFFFFFFF; //(for 32 bit)
for ( NSDictionary *dict in contentArray )
{
NSUInteger newX = [[dict objectForKey:@"x"] integerValue];
NSUInteger newY = [[dict objectForKey:@"y"] integerValue];
if (maxX > newX) maxX = newX;
if (minX > newX) minX = newX;
if (maxY > newY) maxY = newY;
if (minY > newY) minX = newY;
}
如果你有NSDictionary中的对象的NSMutableArray可以使用这样的:
-(float)findMax:array arrayKey:obj {
float max = [[[array objectAtIndex:0] objectForKey:obj] floatValue];
for ( NSDictionary *dict in array ) {
if(max<[[dict objectForKey:obj] floatValue])max=[[dict objectForKey:obj] floatValue];
}
return max;
}
-(float)findMin:array arrayKey:obj {
float min = [[[array objectAtIndex:0] objectForKey:obj] floatValue];
for ( NSDictionary *dict in array ) {
if (min > [[dict objectForKey:obj] floatValue])min = [[dict objectForKey:obj] floatValue];
}
return min;
}
您会如果访问方法,这样在其他类:
GraphData *c=[[GraphData alloc] init];
float maxY=[c findMax:plotData arrayKey:[NSNumber numberWithInt:1]]; //1 or 0 depending on axis
[c release];
//这给出最大和最小值中NSMutableArrray - (无效)FindingMinAndMaxValueInNSMutableArray {
NSMutableArray *array=[[NSMutableArray alloc]initWithObjects:@"0.987",@"0.951",@"0.881",@"0.784",@"0.662",@"0.522",@"0.381",@"-0.265",@"-0.197", @"0.189",@"-0.233",@"0.310",@"0.402",@"0.402",@"0.988",@"0.633",@"0.661",@"0.656",@"0.617",@"0.634",@"0.690",@"0.767",@"0.836",nil];
NSLog(@"The Array Value is %@",array);
NSLog(@"The Array Count is %lu",(unsigned long)array.count);
NSNumber *maxValue = [array valueForKeyPath:@"@max.doubleValue"];
NSLog(@"The maxValue is %@",maxValue);
NSString *str=[NSString stringWithFormat:@"%@",maxValue];
NSInteger path=[array indexOfObject:str];
NSIndexPath *indexpath=[NSIndexPath indexPathForItem:path inSection:0];
NSLog(@"Max Value = %@ and index = %ld",maxValue,(long)indexpath.row);
NSNumber *minValue = [array valueForKeyPath:@"@min.doubleValue"];
NSLog(@"The minValue is %@",minValue);
NSString *str1 = [NSString stringWithFormat:@"%@",minValue];
NSInteger path1 = [array indexOfObject:str1];
NSIndexPath *indexPath1 = [NSIndexPath indexPathForItem:path1 inSection:0];
NSLog(@"Min Value =%@ and index = %ld",minValue,(long)indexPath1.row);
}
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