//一般數學統計
~~~
NSArray *array = @[@"10", @"23", @"43", @"54", @"7", @"17", @"5"];
CGFloat sum = [[array valueForKeyPath:@"@sum.floatValue"] floatValue];
CGFloat avg = [[array valueForKeyPath:@"@avg.floatValue"] floatValue];
CGFloat max =[[array valueForKeyPath:@"@max.floatValue"] floatValue];
CGFloat min =[[array valueForKeyPath:@"@min.floatValue"] floatValue];
NSLog(@"sum==%f\navg==%f\nmax==%f\nmin==%f",sum,avg,max,min);
return [NSString stringWithFormat:@"%f",sum];
~~~
