求数组的平均值、最大值、最小值、总和

    NSMutableArray *array = [NSMutableArray arrayWithObjects:@"1",@"5",@"6.8",@"9.2", nil];
    float sum = [[array valueForKeyPath:@"@sum.floatValue"] floatValue];
    float max = [[array valueForKeyPath:@"@max.floatValue"] floatValue];
    float min = [[array valueForKeyPath:@"@min.floatValue"] floatValue];
    float avg = [[array valueForKeyPath:@"@avg.floatValue"] floatValue];
    NSLog(@"sum=%f\n max=%f\n min=%f\n avg=%f",sum,max,min,avg);

2018-05-31 15:08:50.918941+0800 YCButton[27366:2852035] sum=22.000000
 max=9.200000
 min=1.000000
 avg=5.500000