Layers in a layer array or layer graph pass data to subsequent layers as formatted dlarray
objects. The format of a dlarray
object is a string of characters, in which each character describes the corresponding dimension of the data. The formats consists of one or more of these characters:
"S"
— Spatial
"C"
— Channel
"B"
— Batch
"T"
— Time
"U"
— Unspecified
For example, 2-D image data represented as a 4-D array, where the first two dimensions
correspond to the spatial dimensions of the images, the third dimension corresponds to the
channels of the images, and the fourth dimension corresponds to the batch dimension, can be
described as having the format "SSCB"
(spatial, spatial, channel,
batch).
You can interact with these dlarray
objects in automatic differentiation workflows such as developing a custom layer, using a functionLayer
object, or using the forward
and predict
functions with dlnetwork
objects.
This table shows the supported input formats of FlattenLayer
objects and the corresponding output format. If the output of the layer is passed to a custom layer that does not inherit from the nnet.layer.Formattable
class, or a FunctionLayer
object with the Formattable
property set to 0
(false), then the layer receives an unformatted dlarray
object with dimensions ordered corresponding to the formats in this table.
Input Format | Output Format |
---|
"CB" (channel, batch)
| "CB" (channel, batch)
|
"SCB" (spatial, channel, batch)
|
"SSCB" (spatial, spatial, channel,
batch)
|
"SSSCB" (spatial, spatial, channel,
batch)
|
"CBT" (channel, batch, time)
| "CBT" (channel, batch,
time)
|
"SCBT" (spatial, channel, batch,
time)
|
"SSCBT" (spatial, spatial, channel, batch,
time)
|
"SSSCBT" (spatial, spatial, spatial, channel, batch,
time)
|
"CU" (channel, unspecified)
| "CU" (channel,
unspecified)
|
"SC" (spatial, channel)
|
"SSC" (spatial, spatial, channel)
|
"SSSC" (spatial, spatial, spatial,
channel)
|
In dlnetwork
objects, FlattenLayer
objects also support
these input and output format combinations.
Input Format | Output Format |
---|
"CT" (channel, time)
| "CT" (channel, time)
|
"SCT" (spatial, channel, time)
|
"SSCT" (spatial, spatial, channel,
time)
|
"SSSCT" (spatial, spatial, spatial, channel,
time)
|