Calculate histogram data

histogram.m

- (void)getMax:(float *)max min:(float *)min on:(NSArray *)arr {
    for (NSNumber *num in arr) {
        *max = MAX(*max, num.floatValue);
        *min = MIN(*min, num.floatValue);
    }
}

- (int)indexForResponse:(float)response max:(float)max min:(float)min bucketCount:(int)count {
    float bucketWidth = (max - min) / count;
    return floorf((response - min) / bucketWidth);
}