Statistics is a Foundation framework for calculating—no points for guessing it—statistics. It is inspired by Perl's Statistics::Descriptive and like it consists of two main classes.
SBStatistics calculates a range of statistical measurements on the fly as each data point is added. The data is then immediately discarded, giving it a very low memory footprint.
SBFullStatistics in turn subclasses SBStatistics and records each data point. It is therefore able to provide more advanced statistical functions. The trade-off is that it can consume a lot of memory if you are collecting a lot of data.
The following example assumes you have included the @p Statistics/Statistics.h header and somehow linked to the Statistics framework:
// Create statistics object SBStatistics *stat = [SBStatistics new]; // Add some random data points for (int i = 0; i < 1000; i++) [stat addData:[NSNumber numberWithInt:random()/1000.0]]; // Format report id fmt = [NSMutableArray array]; [fmt addObject:@"Data set consists of %u data points."]; [fmt addObject:@" * Min: %f"]; [fmt addObject:@" * Max: %f"]; [fmt addObject:@" * Mean: %f"]; [fmt addObject:@" * Variance: %f"]; [fmt addObject:@" * StdDev: %f"]; // Print it NSLog([fmt componentsJoinedByString:@"\n"], stat.count, stat.min, stat.max, stat.mean, [stat variance], [stat standardDeviation] );
The SBFullStatistics class can do other interesting stuff:
// Create statistics object SBFullStatistics *stat = [SBFullStatistics new]; // Add some random data. for (int i = 0; i < 1e4; i++) [stat addData:[NSNumber numberWithDouble:random()]]; // Produce 10 equally-sized buckets covering the entire range id buckets = [stat bucketsWithCount:10]; // Calculate frequency distributions. id freq = [stat frequencyDistributionWithBuckets:buckets cumulative:NO]; id cfreq = [stat frequencyDistributionWithBuckets:buckets cumulative:YES]; // Iterate over the buckets and output the values for (id bucket in buckets) NSLog(@"%@ => %@ => %@", bucket, [freq objectForKey:bucket], [cfreq objectForKey:bucket]);
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