这里是目标C
YFRNiceScale.h
#import <Foundation/Foundation.h>
@interface YFRNiceScale : NSObject
@property (nonatomic, readonly) CGFloat minPoint;
@property (nonatomic, readonly) CGFloat maxPoint;
@property (nonatomic, readonly) CGFloat maxTicks;
@property (nonatomic, readonly) CGFloat tickSpacing;
@property (nonatomic, readonly) CGFloat range;
@property (nonatomic, readonly) CGFloat niceRange;
@property (nonatomic, readonly) CGFloat niceMin;
@property (nonatomic, readonly) CGFloat niceMax;
- (id) initWithMin: (CGFloat) min andMax: (CGFloat) max;
- (id) initWithNSMin: (NSDecimalNumber*) min andNSMax: (NSDecimalNumber*) max;
@end
YFRNiceScale.m
#import "YFRNiceScale.h"
@implementation YFRNiceScale
@synthesize minPoint = _minPoint;
@synthesize maxPoint = _maxPoint;
@synthesize maxTicks = _maxTicks;
@synthesize tickSpacing = _tickSpacing;
@synthesize range = _range;
@synthesize niceRange = _niceRange;
@synthesize niceMin = _niceMin;
@synthesize niceMax = _niceMax;
- (id)init {
self = [super init];
if (self) {
}
return self;
}
- (id) initWithMin: (CGFloat) min andMax: (CGFloat) max {
if (self) {
_maxTicks = 10;
_minPoint = min;
_maxPoint = max;
[self calculate];
}
return [self init];
}
- (id) initWithNSMin: (NSDecimalNumber*) min andNSMax: (NSDecimalNumber*) max {
if (self) {
_maxTicks = 10;
_minPoint = [min doubleValue];
_maxPoint = [max doubleValue];
[self calculate];
}
return [self init];
}
/**
* Calculate and update values for tick spacing and nice minimum and maximum
* data points on the axis.
*/
- (void) calculate {
_range = [self niceNumRange: (_maxPoint-_minPoint) roundResult:NO];
_tickSpacing = [self niceNumRange: (_range/(_maxTicks - 1)) roundResult:YES];
_niceMin = floor(_minPoint/_tickSpacing) * _tickSpacing;
_niceMax = ceil(_maxPoint/_tickSpacing) * _tickSpacing;
_niceRange = _niceMax - _niceMin;
}
/**
* Returns a "nice" number approximately equal to range Rounds the number if
* round = true Takes the ceiling if round = false.
*
* @param range
* the data range
* @param round
* whether to round the result
* @return a "nice" number to be used for the data range
*/
- (CGFloat) niceNumRange:(CGFloat) aRange roundResult:(BOOL) round {
CGFloat exponent;
CGFloat fraction;
CGFloat niceFraction;
exponent = floor(log10(aRange));
fraction = aRange/pow(10, exponent);
if (round) {
if (fraction < 1.5) {
niceFraction = 1;
} else if (fraction < 3) {
niceFraction = 2;
} else if (fraction < 7) {
niceFraction = 5;
} else {
niceFraction = 10;
}
} else {
if (fraction <= 1) {
niceFraction = 1;
} else if (fraction <= 2) {
niceFraction = 2;
} else if (fraction <= 5) {
niceFraction = 2;
} else {
niceFraction = 10;
}
}
return niceFraction * pow(10, exponent);
}
- (NSString*) description {
return [NSString stringWithFormat:@"NiceScale [minPoint=%.2f, maxPoint=%.2f, maxTicks=%.2f, tickSpacing=%.2f, range=%.2f, niceMin=%.2f, niceMax=%.2f]", _minPoint, _maxPoint, _maxTicks, _tickSpacing, _range, _niceMin, _niceMax ];
}
@end
使用同样的事情:
YFRNiceScale* niceScale = [[YFRNiceScale alloc] initWithMin:0 andMax:500];
NSLog(@"Nice: %@", niceScale);
最小值和最大值始终是蜱或最低/最高蜱是下一个较小/较高的好数字? – Thomas 2011-12-14 15:35:36
@Thomas在我的情况下,最小滴答总是0,最高滴答应该是下一个更好的数字 – 2011-12-14 15:47:29