/*
* QDataSet.java
*
* Created on January 25, 2007, 9:12 PM
*
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
*/
package org.das2.qds;
/**
*
QDataSets are less abstract and more flexible data model for das2. das2's
* old data model was developed to deliver spectrogram time series data sets
* where the dataset structure would change over time, and the interface is highly
* optimized for that environment. It's difficult to express many datasets in these
* terms, so the simpler "quick" QDataSet was introduced.
*
* The QDataSet can be thought of as a fast java array that has name-value metadata
* attached to it. These arrays of data can have arbitrary rank, although currently
* the interface limits rank to 0,1,2,3, and 4. (Rank N is proposed but not
* developed.) Each dimension's length can vary, like Java arrays, and datasets
* where the dimensions do not vary in length are colloquially called "Qubes."
*
* QDataSets can have other QDataSets as property values, for example the property
* QDataSet.DEPEND_0 indicates that the values are dependent parameters of the "tags"
* QDataSet found there. This how how we get to the same abstraction level of
* the legacy Das2 dataset.
*
* This is inspired by the CDF data model and PaPCo's dataset model.
*
* @see http://autoplot.org/QDataSet
* @author jbf
*/
public interface QDataSet {
/**
* type QDataSet, this dataset is a dependent parameter of the independent parameter represented in this DataSet.
* The tags for the DataSet's 0th index are identified by this tags dataset.
*/
public final static String DEPEND_0="DEPEND_0";
/**
* type QDataSet, this dataset is a dependent parameter of the independent parameter represented in this DataSet.
* The tags for the DataSet's 1st index are identified by this tags dataset. When DEPEND_1 is rank 2,
* then its first dimension goes with DEPEND_0 and its second are the tags for the second dimension.
*/
public final static String DEPEND_1="DEPEND_1";
/**
* type QDataSet, this dataset is a dependent parameter of the independent parameter represented in this DataSet.
* The tags for the DataSet's 2nd index are identified by this tags dataset. When DEPEND_2 is rank 2,
* then it's first dimension goes with DEPEND_0 and it's second are the tags for the second dimension.
*/
public final static String DEPEND_2="DEPEND_2";
/**
* type QDataSet, this dataset is a dependent parameter of the independent parameter represented in this DataSet.
* The tags for the DataSet's 3nd index are identified by this tags dataset. When DEPEND_3 is rank 2,
* then it's first dimension goes with DEPEND_0 and it's second are the tags for the second dimension.
*/
public final static String DEPEND_3="DEPEND_3";
/**
* type QDataSet describing each of the bundled datasets (Bundle Descriptor). This dataset describes
* how the columns should be split up
* into separate parameters. This rank 2 dataset has a length that is equal to the number
* of bundled datasets. The values(i,*) are the qube dimensions of the dataset,
* except for the first dimension. When all the bundled datasets are rank 1, then
* length(*) will be equal to zero. property(*,UNITS) will yield the unit for each
* dataset. Bundle dimensions generally add one physical dimension for each
* bundled dataset. property(*,DEPEND_0) is special, because it will return a string
* rather than a QDataSet. This string should refer to one of the bundled datasets by
* its NAME property. (Any property that returns a QDataSet should return a
* string referring to another dataset in the bundle.) Also the dataset is necessarily
* a QUBE.
*/
public final static String BUNDLE_1="BUNDLE_1";
/**
* type QDataSet describing each position of the rank 1 dataset (Bundle Descriptor). This dataset describes how the columns should be split up
* into separate parameters. See BUNDLE_1. Note slicing a dataset on the zeroth
* dimension will move BUNDLE_1 to BUNDLE_0.
* Properties defined in this dataset will be overwritten by the BUNDLE dataset's properties.
* For example, if the dataset has property( UNITS, 0 ) defined as "Hz" but the
* bundle has property( UNITS,0 ) as "Hertz" then "Hertz" is used.
*/
public final static String BUNDLE_0="BUNDLE_0";
/**
* type QDataSet Bundle Descriptor. When multiple BUNDLES are present, they must be simple bundles, bundling just
* rank 1 datasets.
*/
public final static String BUNDLE_2="BUNDLE_2";
/**
* type QDataSet Bundle Descriptor. When multiple BUNDLES are present, they must be simple bundles, bundling just
* rank 1 datasets.
*/
public final static String BUNDLE_3="BUNDLE_3";
/**
* type Integer, only found in a bundle descriptor (BUNDLE_0 or BUNDLE_1), this returns the integer
* index of the start of the current dataset. If this is null, then the index used to access
* the value may be used. (E.g. a bundle of Rank 1 datasets.)
*/
public final static String START_INDEX="START_INDEX";
/**
* type String which is a comma-delimited list of keywords that describe the boundary
* type for each column. For example, "min,max" "min,maxInclusive" or "c95min,mean,c95max".
* A bins dimension doesn't add a physical dimension. Autoplot uses just "min,max" and "min,maxInclusive"
*/
public final static String BINS_1="BINS_1";
/**
* type String which is a comma-delimited list of keywords that describe the boundary
* type for each column. This comma-delimited list of keywords that describe the boundary
* type for each column. For example, "min,max" "min,maxInclusive" or "c95min,mean,c95max".
* A bins dimension doesn't add a physical dimension. Autoplot uses just "min,max" and "min,maxInclusive"
*/
public final static String BINS_0="BINS_0";
/**
* type String, non-null string identifies that elements in this dimension are
* instances of data with the same dimensions. ds[2,20] where JOIN_0="DEPEND_1" should
* be equivalent to ds[40]. It's not clear if the text should indicate anything, but
* for now let's just indicate the next dimension.
*/
public final static String JOIN_0="JOIN_0";
/**
* type QDataSet, a correlated plane of data. An additional dependent DataSet that is correlated by the first index.
* Note "0" is just a count, and does not refer to the 0th index. All correlated datasets must be
* correlated by the first index. TODO: what about two rank 2 datasets?
* Note that if PLANE_i==null then PLANE_(i+1) must also be null.
*/
public final static String PLANE_0= "PLANE_0";
/**
* type QDataSet, that stores the position of a slice or range in
* a collapsed dimension. In "Flux(Energy) @ Time=2009-03-16T11:19 UT", the Time=... comes from
* a context property. Note "0" is just a count, and does not refer to the 0th index.
* A dataset can have any number of contexts:
* Temperature @ ( Time, Long, Lat ): 37 deg F @ ( 2009-03-16T11:19 UT, 91.5331 deg West, 41.6579 deg North )
* Typically this will be a rank 0 dataset, but may also be a rank 1 dataset with a bins dimension.
*/
public final static String CONTEXT_0= "CONTEXT_0";
/**
* type QDataSet, that stores the position of a slice or range in
* a collapsed dimension. In "Flux(Energy) @ Time=2009-03-16T11:19 UT", the Time=... comes from
* a context property. Note "1" is just a count, and does not refer to the 1th index.
* A dataset can have any number of contexts:
* Temperature @ ( Time, Long, Lat ): 37 deg F @ ( 2009-03-16T11:19 UT, 91.5331 deg West, 41.6579 deg North )
* Typically this will be a rank 0 dataset, but may also be a rank 1 dataset with a bins dimension.
*/
public final static String CONTEXT_1= "CONTEXT_1";
/**
* the maximum number of allowed planes. This should be used to enumerate all the planes.
*/
public final static int MAX_PLANE_COUNT=50;
/**
* maximum number of same-unit bundled dimensions (e.g. B_GSM[time,Bundle]). This was introduced when cdf dataset
* fa_k0_tms_20040224_v01.cdf?O+_en had 48 energy channels, was marked as time_series but wouldn't render because
* view code limited to 12.
*
* Seth's file vap+cdf:file:///home/jbf/ct/hudson/data.backup/cdf/lanl/rbspa_pre_ect-mageisHIGH-sp-L1_20130213_v1.0.0.cdf?Count_Rate_elec
* RBSP/Hope has 72 channels.
*/
public final static int MAX_UNIT_BUNDLE_COUNT=96;
/**
* the highest rank supported by the library. Arbitrary high rank datasets are supported through
* RankNDataSet, but must be sliced to be accessed.
*/
public static int MAX_RANK=4;
/**
* the highest rank supported by the library, without direct access
* to datums. Some codes may choose to use this when supporting high rank
* data is trivial.
*/
public static int MAX_HIGH_RANK=8;
/**
* type Units indicating the units of the dataset in the enumeration of
* org.das2.datum.Units, as in org.das2.datum.Units.km. New unit types
* can be introduced with Units.lookup. For example,
*
*from org.das2.datum import Units
*u= Units.lookupUnits('seconds since 2015-001T00:00')
*ds= findgen(3600)
*ds= putProperty( ds, QDataSet.UNITS, u )
*plot( ds ) # plots line from 00:00 to 01:00.
*
* @see org.das2.datum.Units
*/
public final static String UNITS="UNITS";
/**
* type String, Java/C format string for formatting the values. This
* should imply precision, and codes that serialize data can use this
* to correctly format the data. Examples include:
* - %d integers
* - %5.1f floats with one decimal place
* - %.3e exponential notation
* - %x hex of the integer
*
*/
public final static String FORMAT="FORMAT";
/**
* type Number, value to be considered fill (invalid) data. Note because
* all data is accessed as doubles, noise may be inadvertently affect numbers.
*/
public final static String FILL_VALUE="FILL_VALUE";
/**
* type Number, minimum bounding measurements to be considered valid. Lower
* and Upper bounds are inclusive. FILL_VALUE should be used to make the
* lower bound or upper bound exclusive. Note DatumRange contains logic is
* exclusive on the upper bound.
*/
public final static String VALID_MIN="VALID_MIN";
/**
* type Number, maximum bounding measurements to be considered valid. Lower
* and Upper bounds are inclusive. FILL_VALUE should be used to make the
* lower bound or upper bound exclusive. Note DatumRange contains logic is
* exclusive on the upper bound.
*/
public final static String VALID_MAX="VALID_MAX";
/**
* type Number that is min used to discover datasets. This should be a reasonable representation
* of the expected dynamic range of the dataset.
*/
public final static String TYPICAL_MIN="TYPICAL_MIN";
/**
* type Number that is the max used to discover datasets. This should be a reasonable representation
* of the expected dynamic range of the dataset.
*/
public final static String TYPICAL_MAX="TYPICAL_MAX";
/**
* String, "linear" or "log", hinting at the preference for linear or a log
* axis.
*/
public final static String SCALE_TYPE="SCALE_TYPE";
/**
* String, Concise Human-consumable label suitable for a plot label (~10 chars).
*/
public final static String LABEL="LABEL";
/**
* String, Human-consumable string suitable for a plot title (~100 chars).
*/
public final static String TITLE="TITLE";
/**
* String, Human-consumable string suitable for describing the data more fully.
* This should be html text, or just a link to other documentation (one URL,
* or two sentences to one page of text).
*/
public final static String DESCRIPTION="DESCRIPTION";
/**
* QDataSet, dataset of same geometry that indicates the weights for each point. Often weights are computed
* in processing, and this is where they should be stored for other routines. When the weights plane is
* present, routines can safely ignore the FILL_VALUE, VALID_MIN, and VALID_MAX properties, and use non-zero weight to
* indicate valid data. Further, averages of averages will compute accurately.
*/
public final static String WEIGHTS="WEIGHTS";
/**
* Boolean, Boolean.TRUE if dataset is monotonically increasing, and the data is rank 1.
* Data may only contain invalid values at the beginning or end, and may contain repeated
* values. Generally this will be used with tags datasets.
*/
public final static String MONOTONIC="MONOTONIC";
/**
* QDataSet of rank0, which is the expected distance between successive
* measurements where it is valid to make inferences about the data.
* For example, interpolation is disallowed for points 1.5*CADENCE apart.
* This property only makes sense with a tags dataset. Note this may be
* a "ratiometric" datum, like 110 percentIncrease, for logarithmically
* spaced data. Cadence must be positive.
*/
public final static String CADENCE="CADENCE";
/**
* QDataSet of rank 0, or correlated QDataSet that limits accuracy. This should
* be interpreted as the one standard deviation confidence level, and must
* be positive.
* @see #BIN_PLUS for measurement intervals.
*/
public final static String DELTA_PLUS="DELTA_PLUS";
/**
* QDataSet of rank 0, or correlated QDataSet that limits accuracy. This should
* be interpreted as the one standard deviation confidence level, and must
* be positive.
* @see #BIN_MINUS for measurement intervals.
*/
public final static String DELTA_MINUS="DELTA_MINUS";
/**
* QDataSet of rank 0 or correlated QDataSet identifies boundary. This is added to the
* measurements and should be interpreted as the upper limit of 100% confidence
* interval where a measurement was collected.
* Note if both DELTA_PLUS and BIN_PLUS are found,
* then BIN_PLUS must be greater than DELTA_PLUS.
* @see #DELTA_PLUS for one-standard deviation confidence interval.
*/
public final static String BIN_PLUS="BIN_PLUS";
/**
* QDataSet of rank 0 or correlated QDataSet identifies boundary. This is subtracted from the
* measurements and should be interpreted as the lower limit of the 100% confidence interval where a measurement was collected.
* @see #DELTA_MINUS for one-standard deviation confidence interval.
*/
public final static String BIN_MINUS="BIN_MINUS";
/**
* QDataSet of rank 1 identifies boundary in the same units as the dataset.
* This should be interpreted as the upper limit of 100% confidence
* interval where a measurement was collected. When this is found, BIN_PLUS
* and BIN_MINUS should be ignored.
* @see #BIN_PLUS which is the offset.
*/
public final static String BIN_MAX="BIN_MAX";
/**
* QDataSet of rank 1 identifies boundary in the same units as the dataset.
* This should be interpreted as the lower limit of the 100% confidence
* interval where a measurement was collected. When this is found, BIN_PLUS
* and BIN_MINUS should be ignored.
* @see #BIN_MINUS which is the offset.
*/
public final static String BIN_MIN="BIN_MIN";
/**
* CacheTag, indicating the coverage and resolution of a dimension. This is
* an object that represents
* the coverage and resolution of the interval covered. For example, in Autoplot
* the TimeSeriesBrowse uses this to keep track of what's already been read.
*/
public final static String CACHE_TAG="CACHE_TAG";
/**
* String, hint as to preferred rendering method. Examples include "spectrogram", "time_series", and "stack_plot",
* "nnSpectrogram", "hugeScatter", "series", "scatter", "colorScatter", "stairSteps", "fillToZero"
* "digital", "image", "pitchAngleDistribution", "eventsBar". Note these are just suggestions and are not
* interpreted in the library.
*/
public final static String RENDER_TYPE="RENDER_TYPE";
/**
* full-fidelity rendering of buckshot and connect-a-dot plots
*/
public final static String VALUE_RENDER_TYPE_SERIES="series";
/**
* use blocks to draw each point, so data extents can be seen.
*/
public final static String VALUE_RENDER_TYPE_NNSPECTROGRAM="nnSpectrogram";
/**
* draw events bars
*/
public final static String VALUE_RENDER_TYPE_EVENTS_BAR="eventsBar";
/**
* values are drawn.
*/
public final static String VALUE_RENDER_TYPE_DIGITAL="digital";
/**
* values are an RGB image, a rank 3 dataset [w,h,3] or [w,h,4]. The
* "3" should be R,G, and B channels, and when "4" is used, ARGB is the
* default. There can be a DEPEND_2 that is a QDataSet with ordinal data,
* specifying the channels like so Ops.labelsDataset(['a','b','g','r']) or
* Ops.labelsDataset(['a','b','g','r']). Only bgr or rgb models are supported
* in the RGBImageRenderer, but future versions could support other color
* models.
*/
public final static String VALUE_RENDER_TYPE_COMPOSITE_IMAGE="image";
/**
* String, a java identifier that should can be used when an identifier is needed. This is
* originally introduced for debugging purposes, so datasets can have a concise, meaningful name
* that is decoupled from the label. When NAMEs are used, properties with the same
* name should only refer to the named dataset.
*/
public final static String NAME="NAME";
/**
* Boolean.TRUE indicates that the dataset is a "qube," meaning
* that all dimensions have fixed length and certain optimizations and
* operators are allowed. Note that when DEPEND_1 is a rank 1 dataset,
* this implies QUBE. Likewise BUNDLE_1 is a qube.
* Note the result of any slice must be a qube.
*/
public final static String QUBE="QUBE";
/**
* String, representing the coordinate frame of the vector index. The units
* of a dataset should be EnumerationUnits which convert the data in this
* dimension to dimension labels that are understood in the coordinate frame
* label context. (E.g. X,Y,Z in GSM.)
* (Note this is before BUNDLE dimensions were formalized and is not used.)
*/
public final static String COORDINATE_FRAME="COORDINATE_FRAME";
/**
* Map<String,Object> representing additional properties used by client codes. No
* interpretation is done of these properties, but they are passed around as much
* as possible. Note Object can be String, Double, or Map<String,Object>. METADATA_MODEL
* is a string identifying the type of metadata,
* a scheme for the metadata tree, such as ISTP-CDF or SPASE.
*/
public final static String METADATA="METADATA";
/**
* String, a scheme for the metadata tree, such as ISTP or SPASE. This should identify
* a node's type when the node is present, but should not require that the node
* be present. When a required node is missing, this should be treated as if
* none of the metadata is available. This logic is to support aggregating
* metadata.
*/
public final static String METADATA_MODEL="METADATA_MODEL";
/**
* the metadata is ISTP-CDF metadata
*/
public final static String VALUE_METADATA_MODEL_ISTP="ISTP-CDF";
/**
* the metadata is SPASE (Space Physics Archive Search Extract)
*/
public final static String VALUE_METADATA_MODEL_SPASE="SPASE";
/**
* the value is a complex number, having two elements, the first is real second is imaginary.
*/
public final static String VALUE_COORDINATE_FRAME_COMPLEX_NUMBER="ComplexNumber";
/**
* String, human consumable identifying data version. Presently this
* is intended for human consumption, but eventually we may make them usable
* by software as well. Note if multiple versions go into making a product
* (e.g. aggregation), the version string should contain space-delimited
* version ids, so note versions must not contain spaces for other purposes.
* Also two version strings containing the same value can be coalesced. If this
* is prefixed with "<scheme>:", then this is to be interpreted as such:
* - sep: period-delimited list of numeric sorted: 2.2.0 < 2.15.2 < 10.2.0
*
- alpha: alpha-numeric sorted: 20030202B>20030202A
*
* otherwise it should be numerically sorted.
* (see org.das2.fsm.FileStorageModel)
*/
public final static String VERSION="VERSION";
/**
* String, Human-consumable string identifying the source of a dataset, such as the file or URI from
* which it was read. Clearly this is easily lost as processes are applied to the
* data, but when no other source is involved in a process (excluding library code
* itself), then the source should be preserved.
*/
public final static String SOURCE="SOURCE";
/**
* QDataSet of events scheme, containing a list of messages encountered during processing that annotate the data.
* For example, the AggregatingDataSource in Autoplot would add an event to the dataset when a file could not be used.
* This is a rank 2 dataset with BUNDLE_1=startTime,stopTime,message for now, but may soon allow for bounding qubes:
* BUNDLE_1=startTime,stopTime,startEn,stopEn,message, and this should be visualized via the EventsRenderer.
*/
public final static String NOTES="NOTES";
/** Bundle Descriptor properties */
/**
* String, the name of another dataset in the bundle descriptor. Before this was introduced,
* a BundleDescriptor could have DEPEND_0 be a string.
*/
public final static String DEPENDNAME_0="DEPENDNAME_0";
/**
* String, the name of another dataset in the bundle descriptor. Before this was introduced,
* a BundleDescriptor could have DEPEND_1 be a string. Note this should only be used if
* DEPEND_1 is rank 2, otherwise the dataset should be a property of DEPEND_1.
*/
public final static String DEPENDNAME_1="DEPENDNAME_1";
/**
* String, the name of the rank 2 or more dataset in a bundle descriptor.
*/
public final static String ELEMENT_NAME="ELEMENT_NAME";
/**
* String, the label of the rank 2 or more dataset in a bundle descriptor.
*/
public final static String ELEMENT_LABEL="ELEMENT_LABEL";
/**
* int array, the dimensions of the element. A rank 0 is implicitly [],
* a rank 1, n by 1, would be [1]. This is similar to the size command, for
* one record of the data.
* @see org.das2.qds.ops.Ops#size(org.das2.qds.QDataSet)
*/
public final static String ELEMENT_DIMENSIONS="ELEMENT_DIMENSIONS";
/**
* Map<String,Object> representing additional properties used by client codes. No
* interpretation is done of these properties, but they are passed around as much
* as possible. The object values should be but don't have to be limited to: double, double array,
* datum, QDataSet, String, String array.
*/
public final static String USER_PROPERTIES="USER_PROPERTIES";
/**
* typical bin is min,max with min inclusive and max exclusive.
*/
public static String VALUE_BINS_MIN_MAX="min,max";
/**
* scale type to suggest log axes and bins.
*/
public static String VALUE_SCALE_TYPE_LOG="log";
/**
* scale type to suggest linear axes and bins.
*/
public static String VALUE_SCALE_TYPE_LINEAR="linear";
/**
* the minimum length of each of the waveform packets in a rank 2 waveform dataset.
*/
public static int MIN_WAVEFORM_LENGTH=32;
/**
* the fill value often used in codes.
*/
public static double DEFAULT_FILL_VALUE= -1e31;
/**
* returns the rank of the dataset, which is the number of indeces used to access data. Only rank 0, 1, 2, 3, and 4 datasets
* are supported in the interface. When a dataset's rank is 5 or greater, it should implement the HighRankDataSet interface
* which affords a slice operation to reduce rank.
* @return the rank, or number of indeces used to access data.
*/
int rank();
/**
* rank 0 accessor.
* @throws IllegalArgumentException if the dataset is not rank 0.
* @return the value, see the property UNITS to interpret this.
*/
double value();
/**
* rank 0 accessor which provides the string value
* @throws IllegalArgumentException if the dataset is not rank 0.
* @return the value, see the property UNITS to interpret this.
*/
String svalue();
/**
* rank 1 accessor.
* @param i the index
* @return the value, see the property UNITS to interpret this.
* @throws IllegalArgumentException if the dataset is not rank 1.
*/
double value( int i );
/**
* rank 2 accessor.
* @param i0 the index
* @param i1 the index
* @return the value, see the property UNITS to interpret this.
* @throws IllegalArgumentException if the dataset is not rank 2.
*/
double value( int i0, int i1 );
/**
* rank 3 accessor.
* @param i0 the index
* @param i1 the index
* @param i2 the index
* @return the value, see the property UNITS to interpret this.
* @throws IllegalArgumentException if the dataset is not rank 3.
*/
double value( int i0, int i1, int i2 );
/**
* rank 4 accessor.
* @param i0 the index
* @param i1 the index
* @param i2 the index
* @param i3 the index
* @return the value, see the property UNITS to interpret this.
* @throws IllegalArgumentException if the dataset is not rank 4.
*/
double value( int i0, int i1, int i2, int i3);
/**
* accessor for properties attached to the dataset. See final static members
* for example properties.
* @param name property name, such as "DEPEND_0" or "UNITS"
* @return the value
* @see #DEPEND_0
* @see #UNITS
*/
Object property( String name );
/**
* accessor for properties attached to the dataset's first index. These properties
* override (or shadow) properties attached to the dataset, and often implementations
* will simply return the result of the no-index accessor.
*
* Note: properties of higher dimension are accessible only by slicing.
* @param name property name, such as "DEPEND_0" or "UNITS"
* @param i the index
* @return the value
* @see #DEPEND_0
* @see #UNITS
*/
Object property( String name, int i );
/**
* return the length of the first dimension
* @return the length of the first dimension
*/
int length( );
/**
* return the length of the second dimension, for the ith element of the first dimension. Note
* if there are zero elements in the first dimension, but this is a QUBE, then this should not
* throw an IndexOutOfBoundsException.
* @param i the index
* @return the length of the second dimension at index i.
*/
int length( int i );
/**
* return the length of the third dimension, for the ith element of the first dimension and jth element of the second dimension.
* @param i the index
* @param j the index
* @return the length of the third dimension at index i.
*/
int length( int i, int j );
/**
* return the length of the fourth dimension for the ith, jth and kth elements of the first three dimensions.
* @param i the index
* @param j the index
* @param k the index
* @return the length of the fourth dimension for the ith, jth and kth elements of the first three dimensions.
*/
int length( int i, int j, int k);
/**
* return a dataset that is a slice of this dataset, slicing on the zeroth
* dimension.
* A slice will be the elements at this index, for example if this dataset
* is a rank 2 dataset flux(Time,Energy) then the slice of this will be
* a rank 1 dataset flux(Energy).
* The result of any slice will be a qube.
* @throws IllegalArgumentException when dataset rank is zero.
* @param i the index to slice at
* @return the rank n-1 QDataSet at index i.
*/
QDataSet slice( int i );
/**
* return a dataset that is a subset of this dataset.
* For example:
*
* {@code
* ds= DDataSet.createRank1(100);
* QDataSet trim= ds.trim(50,60);
* assert( trim.length()==10 );
* }
*
* @param start the first index to be included in the new dataset.
* @param end the exclusive index indicating the last index.
* @return a QDataSet with the same rank but fewer elements.
*/
QDataSet trim( int start, int end );
/**
* return null or an object implementing the capability for the given interface
* For example:
*
*ds= DDataSet.createRank1(100);
*WriteCapability write= ds.capability( WriteCapability.class );
*write.putValue( 99, -1e31 );
*
* This allows operations to be performed efficiently. Note there is no WriteCapability class, this is
* just an example.
*
* @param a capability
* @param clazz the class, such as WriteCapability.class
* @return the implementing class, or null (Jython None) if the capability is not provided.
*/
T capability( Class clazz );
}