An MNIST-like fashion product dataset | Hacker News Reader

An MNIST-like fashion product dataset

github.com

220 pointskashifr21 comments

I don't understand why this seems to be getting so much attention. There are plenty of small image datasets around, and wide recognition of the issues with MNIST.

I see no evidence at all that this particular dataset is better than MNIST. None of the issues they themselves list with MNIST are discussed with relation to their proposed replacement.

The benchmarks they provide are entirely useless - sklearn does not claim to be a platform for computer vision models. A quick WRN model gets 96% of this dataset (h/t @ajmooch on Twitter), suggesting that it doesn't deal with the "too easy" issue.

The images clearly don't deal with the problem of lack of translation invariance.

On the downside, they don't have the same ease of understanding of hand-drawn digits, which is extremely helpful for teaching, debugging, and visualizing.

I completely agree. My company does image recognition in fashion and this dataset is both way too easy and not useful. I'd love to see a client with such an easy problem (telling between shoes and bags in inventory images).

We regularly get high 90's accuracy on real world images where the system has to auto-crop all on its own. Inventory images are far too easy.

What's more, the actual hard cases (like tiny shorts vs tiny skirt, or long blouse vs short dress) would be near impossible to do at such low resolution.

Wide residual networks are not exactly hello-world networks. For teaching (I teach a course on DL), I think this is great. It adds variety for me in terms of an introductory tutorial for DL, and it encourage students to use a GPU as error rates will be high on their laptops.

> sklearn does not claim to be a platform for computer vision models.

There are more than a dozen image classification and segmentation examples on the scikit-learn gallery:

http://scikit-learn.org/stable/auto_examples/index.html

Yes but at this stage they're really toy examples. IIRC the best sklearn result they showed on this benchmark had 20% error, whereas the little WRN network was 4%.

IIRC a simple convnet will get higher than 99.0% on MNIST, so maybe it is more difficult than it seems at first glance :)

How would you go about generating such dataset?

1. Scrape images and store as png

2. Downscale to 28px

3. Convert each image to grayscale

4. Convert to matrices and add label (additional row?)

5. Normalize to have matrices of 1 and 0 for faster computation

6. Vectorize said matrices

7. Concatenate into one big vector

Did I miss something / Am I fooling myself?

I plan on working on my first ML side project and I would love to gain some insights from HN.

This might help. Their academic paper is basically a description of how they made the dataset (and why) and includes a great example of the steps they went through to convert the images.

https://arxiv.org/pdf/1708.07747.pdf

That's the right idea overall, with a few caveats.

1. Yes but you need to manually inspect and verify that the images are of the right class

5. Images are grayscale, not only black and white.

Additionally, MNIST and fashion-MNIST have all their objects centered and of similar scale. This is a large part of what makes them a popular first test for any image model: they are very simple to solve as the model need not be very robust to fit the dataset.

> Additionally, MNIST and fashion-MNIST have all their objects centered and of similar scale. This is a large part of what makes them a popular first test for any image model: they are very simple to solve as the model need not be very robust to fit the dataset.

Yeah, this is crucial. Especially when trying to generalize models. It’s easy to verify the usefulness of data augmentation when you can make basic assumptions about the data (e.g. it’s centered).

4. It’s usually preferable if your dependent (target) variable is separate from your independent (output) variable for usability reasons.

5. I’d provide a vector of integers where each integer represents a different class. Encoding is dependent on the underlying algorithm and its implementation. You’d want to provide plenty of flexibility to users.

I’d also add that MNIST has an advantage over a dataset like CIFAR because background pixels are zeroed out (i.e. you don’t need to account for varied backgrounds). So you’d probably want to segment your objects.

Looks like this was sourced from in-house at some German online retailer: zalando.de. There is a similar data set from from amazon sourced by UCSD: http://jmcauley.ucsd.edu/data/amazon/

And our research on recommenders using it: http://sharknado.eggie5.com

Particularly, the 2D scatter of the CNN features: http://sharknado.eggie5.com/tsne

It says in the README, that it's from them (Zalando). Via a Google search, they're an e-commerce site from Berlin funded by the Rocket Internet folks.

I'd love to play around with this dataset! It certainly seems richer than MNIST, and would most likely force the network to extract more features.

But just like MNIST, it seems to lack variety in the positioning of the important elements, they are all centered which means that they don't train the network in being translation invariant. I presume this issue can be tackled with data augmentation techniques like applying affine transformations.

You could potentially add translations to the dataset automatically (and generate mosaics with multiple images). Since you've done the transforms you have perfect knowledge of the new images and they're ready to train on

For a MNIST-like dataset, I often use not-MNIST (http://yaroslavvb.blogspot.com/2011/09/notmnist-dataset.html), which is more difficult than the original one (see examples of misclassified digits here: https://docs.neptune.ml/get-started/character-recognition/).

However, I am not sure if we need more MNIST-like datasets. With small size many things make much less sense (data augmentation, even convnets as images are centered anyway) plus using many channels is a typical things (IRL I rarely work with grayscale images). So I am curious, in which way this dataset is better than CIFAR-10?

See my note on datasets in Learning Deep Learning, http://p.migdal.pl/2017/04/30/teaching-deep-learning.html#da....

If I am understanding the side-by-side comparison correctly, then the performance is highly correlated with MNIST (at least for high accuracy methods).

https://i.imgur.com/viV7gFB.png (x-axis: Fashion, y-axis: MNIST)

They should be correlated. It’s difficult (or near impossible) to interpret the underlying convolutional features, but one can assume they are recognizing basic image descriptors like intensities and shapes. They are rescaled to a size that would deemphasize complex descriptors like texture. Likewise, they are single-channel so that would deemphasize color features.

One of the reasons people have shifted away from MNIST is that it's simply too easy. Single channel, small image size, few classes, etc. Unfortunately, this does not address any of these concerns.

How is this 'better' then cifar10 / cifar100?

From looking at the examples, zeroed out backgrounds are one advantage to CIFAR (depending on your task).

Reply on news.ycombinator.com