Fitting a Support Vector Classifier in scikit-learn with image data produces error - machine-learning

Question

I'm trying to train an SVC classifier for image data. Yet, when I run this code:
classifier = svm.SVC(gamma=0.001)
classifier.fit(train_set, train_set_labels)
I get this error:
ValueError: setting an array element with a sequence.
I produced the images into an array with Matplotlib: plt.imread(image).
The error seems like it's not in an array, yet when I check the types of the data and the labels they're both lists (I manually add to a list for the labels data):
print(type(train_set))
print(type(train_set_labels))
<class 'list'>
<class 'list'>
If I do a plt.imshow(items[0]) then the image shows correctly in the output.
I also called train_test_split from scikit-learn:
train_set, test_set = train_test_split(items, test_size=0.2, random_state=42)
Example input:
train_set[0]
array([[[212, 134, 34],
[221, 140, 48],
[240, 154, 71],
...,
[245, 182, 51],
[235, 175, 43],
[242, 182, 50]],
[[230, 152, 51],
[222, 139, 47],
[236, 147, 65],
...,
[246, 184, 49],
[238, 179, 43],
[245, 186, 50]],
[[229, 150, 47],
[205, 122, 28],
[220, 129, 46],
...,
[232, 171, 28],
[237, 179, 35],
[244, 188, 43]],
...,
[[115, 112, 103],
[112, 109, 102],
[ 80, 77, 72],
...,
[ 34, 25, 28],
[ 55, 46, 49],
[ 80, 71, 74]],
[[ 59, 56, 47],
[ 66, 63, 56],
[ 48, 45, 40],
...,
[ 32, 23, 26],
[ 56, 47, 50],
[ 82, 73, 76]],
[[ 29, 26, 17],
[ 41, 38, 31],
[ 32, 29, 24],
...,
[ 56, 47, 50],
[ 59, 50, 53],
[ 84, 75, 78]]], dtype=uint8)
Example label:
train_set_labels[0]
'Picasso'
I'm not sure what step I'm missing to get the data in the form that the classifier needs in order to train it. Can anyone see what may be needed?

Answer 1

The error message you are receiving:
ValueError: setting an array element with a sequence,
normally results when you are trying to put a list somewhere that a single value is required. This would suggest to me that your train_set is made up of a list of multidimensional elements, although you do state that your inputs are lists. Would you be able to post an example of your inputs and labels?
UPDATE
Yes, it's as I thought. The first element of your training data, train_set[0], corresponds to a long list (I can't tell how long), each element of which consists of a list of 3 elements. You are therefore calling the classifier on a list of lists of lists, when the classifier requires a list of lists (m rows corresponding to the number of training examples with each row made up of a list of n features). What else is in your train_set array? Is the full data set in train_set[0]? If so, you would need to create a new array with each element corresponding to each of the subelements of train_set[0], and then I believe your code should run, although I am not too familiar with that classifier. Alternatively you could try running the classifier with train_set[0].
UPDATE 2
I don't have experience with scikit-learn.svc so I wouldn't be able to tell you what the best way of preprocessing the data in order for it to be acceptable to the algorithm, but one method would be to do as I said previously and for each element of train_set, which is composed of lists of lists, would be to recurse through and place all the elements of sublist into the list above. For example
new_train_set = []
for i in range(len(train_set)):
for j in range(len(train_set[i]):
new_train_set.append([train_set[i,j])
I would then train with new_train_set and the training labels.