I am trying to predict the of number peaks in time series data by using a CNN and keep on getting a data shape error. My data looks as follows:
X
= list of 520 lists (each is a time series) of various lengths (shortest = 137 elements, longest = 2297 elements)y
= list with 520 elements, each being the number of peaks for the respective time series
Due to the various lengths of the time series, I padded X. The shapes of X_train and X_test, after converting them from numpy arrays to tensors are:
X_train.shape
=TensorShape([390, 2297])
X_test.shape
=TensorShape([130, 2297])
I am new to keras and I am very unsure about the input_size in the first Conv1D layer. According to this post (Keras/Tensorflow Conv1D expected input shape) I chose it as (2297, 1)
or (520, 1)
, but none of them works. The documentation of Keras says that the input shape should be (batch_size, feature_size, channels)
, where batch_size
is omitted though.
from sklearn.model_selection import train_test_split import tensorflow as tf from tensorflow import keras from tensorflow.keras.layers import * from tensorflow.keras.optimizers import Adam #for structure of X and y, see explanation above X_padded = tf.keras.preprocessing.sequence.pad_sequences(X) X_train, X_test, y_train, y_test = train_test_split(X_padded, y, test_size=0.25, random_state=33) X_train = tf.convert_to_tensor(X_train) X_test = tf.convert_to_tensor(X_test) y_train = tf.convert_to_tensor(y_train) y_test = tf.convert_to_tensor(y_test) model = keras.Sequential() model.add(Conv1D(filters=16, kernel_size=3, activation = 'relu', strides = 1, padding = 'same', input_shape=(2297, 1))) model.add(Dropout(0.1)) model.add(Conv1D(filters=32, kernel_size=3, activation = 'relu', strides = 1, padding = 'same')) model.add(Dropout(0.2)) model.add(Flatten()) model.add(Dense(9, activation='softmax')) # '9' because there are 9 possible peak counts in the data model.compile(optimizer=Adam(learning_rate = 0.001), loss = 'sparse_categorical_crossentropy', metrics = ['accuracy']) progress = model.fit(X_train, y_train, epochs = 15, validation_data = (X_test, y_test), verbose=1)
Error:
ValueError: Input 0 of layer sequential is incompatible with the layer: expected ndim=3, found ndim=2. Full shape received: [None, 2297]
What might be the issue here?
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Answer
I was able to solve it. The correct input shape is given here Convolutional neural network Conv1d input shape in the answer of user ‘rnso’.
I shaped my X_train and X_test (being numpy.arrays) as
X_train = X_train.reshape(X_train.shape[0], X_train.shape[1], 1) X_test = X_test.reshape(X_test.shape[0], X_test.shape[1], 1)
and stated the input_shape
in the Conv1D
statement as input_shape=(ncols, 1)
input_shape=(2297, 1)