CombinedDatastore

Datastore to combine data read from multiple underlying datastores

Description

Use a CombinedDatastore object to combine the data read from multiple other datastores.

A CombinedDatastore maintains parity between the underlying datastores, so that data is read from corresponding parts of the underlying datastores. Resetting the CombinedDatastore resets all of the underlying datastores.

Creation

You can create a CombinedDatastore object using the combine function. For example, dsnew = combine(ds1,ds2) creates a datastore that combines the read data from datastores ds1 and ds2.

Properties

UnderlyingDatastores — Underlying datastores

cell array

Underlying datastores, specified as a cell array of datastore objects.

Data Types: cell

SupportedOutputFormats — Formats supported for writing

string row vector

This property is read-only.

Formats supported for writing, returned as a row vector of strings. This property specifies the possible output formats when using writeall to write output files from the datastore.

Object Functions

combine	Combine data from multiple datastores
hasdata	Determine if data is available to read
preview	Preview subset of data in datastore
read	Read data in datastore
readall	Read all data in datastore
writeall	Write datastore to files
reset	Reset datastore to initial state
transform	Transform datastore
numpartitions	Number of datastore partitions
partition	Partition a datastore
shuffle	Shuffle all data in datastore
isPartitionable	Determine whether datastore is partitionable
isSubsettable	Determine whether datastore is subsettable
isShuffleable	Determine whether datastore is shuffleable

Examples

Combine Datastores

Create a datastore that maintains parity between the pair of images of the underlying datastores. For instance, create two separate image datastores, and then create a combined datastore that reads corresponding images from the two image datastores.

Create a datastore imds1 representing a collection of three images.

imds1 = imageDatastore({'street1.jpg','street2.jpg','peppers.png'}); 

Create a second datastore imds2 by transforming the images of imds1 to grayscale images.

imds2 = transform(imds1,@(x) im2gray(x));

Create a combined datastore from imds1 and imds2.

imdsCombined = combine(imds1,imds2);

Read the first pair of images from the combined datastore. Each read operation on this combined datastore returns a pair of images represented by a 1-by-2 cell array.

dataOut = read(imdsCombined)

dataOut=1×2 cell array
    {480x640x3 uint8}    {480x640 uint8}

Display the output of the first read from the combined datastore.

imshow(imtile(dataOut));

Version History

Introduced in R2019a