combine

Combine data from multiple datastores

Syntax

dsnew = combine(ds1,ds2,...,dsN)

Description

dsnew = combine(ds1,ds2,...,dsN) combines two or more datastores by horizontally concatenating the data returned by the read function on the input datastores.

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));

Input Arguments

ds1,ds2,...,dsN — Datastores to combine

datastore objects

Datastores to combine, specified as two or more comma separated datastore objects. For a complete list of built-in datastores, see Select Datastore for File Format or Application. You also can specify custom datastores.

Output Arguments

dsnew — New datastore with combined data

CombinedDatastore object

New datastore with combined data, returned as a CombinedDatastore object.

The dsnew object is a new datastore instance that is the horizontally concatenated result of a read operation on each of the underlying datastores.

Extended Capabilities

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

Usage notes and limitations:

• In a thread-based environment, you can use combine only with the following datastores:

  • ImageDatastore objects

  • CombinedDatastore or TransformedDatastore objects you create from ImageDatastore objects by using combine or transform

  You can use combine with other datastores if you have Parallel Computing Toolbox™. To do so, run the function using a process-backed parallel pool instead of using backgroundPool or ThreadPool (use either ProcessPool or ClusterPool).

For more information, see Run MATLAB Functions in Thread-Based Environment.