# MXHistogram An object representing a histogram of data values of the same type of unit. ``` class MXHistogram where UnitType : Unit ``` ## Overview A *histogram* measures the number of times a data point for a variable falls into a specific range of possible values within a set of data. Usually, histograms are depicted as bar charts, in which each bar represents a range of values, and the height of each bar represents the number of times the value of the variable falls within a particular range. In this class, each bar is represented by a *bucket*. A bucket holds the results for a series of measured values, such as all the events occurring between 3 and 5 seconds. MetricKit uses fixed-width buckets that are device-independent with intervals that are based on the type of metric. Use the [`bucketStart`](/documentation/MetricKit/MXHistogramBucket/bucketStart) and [`bucketEnd`](/documentation/MetricKit/MXHistogramBucket/bucketEnd) properties to find the start and end of an interval. The returned results contain only buckets with at least one item so [`bucketEnumerator`](/documentation/MetricKit/MXHistogram/bucketEnumerator) may not return all intervals. For example, if the fixed width for the time to resume the app is 10 ms, then the sequence of buckets is: 0…9 ms, 10…19 ms, 20…29 ms, etc. If there’s data only in the 0…9 ms and 20…29 ms buckets, then the report skips the 10…19 ms bucket. ## Topics ### Reading the buckets [`bucketEnumerator`](/documentation/MetricKit/MXHistogram/bucketEnumerator) An enumerator for the buckets containing the data in the histogram. [`totalBucketCount`](/documentation/MetricKit/MXHistogram/totalBucketCount) The total number of buckets in the histogram. [`MXHistogramBucket`](/documentation/MetricKit/MXHistogramBucket) An object representing a bucket of data in a histogram. ## Relationships ### Conforms To [`CustomDebugStringConvertible`](/documentation/Swift/CustomDebugStringConvertible) [`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol) [`Equatable`](/documentation/Swift/Equatable) [`NSSecureCoding`](/documentation/Foundation/NSSecureCoding) [`CustomStringConvertible`](/documentation/Swift/CustomStringConvertible) [`Hashable`](/documentation/Swift/Hashable) [`NSCoding`](/documentation/Foundation/NSCoding) [`CVarArg`](/documentation/Swift/CVarArg) ### Inherits From [`NSObject-swift.class`](/documentation/ObjectiveC/NSObject-swift.class) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)