Questions tagged [preprocessing]

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40
votes
2answers
37k views

How to prepare/augment images for neural network?

I would like to use a neural network for image classification. I'll start with pre-trained CaffeNet and train it for my application. How should I prepare the input images? In this case, all the ...
10
votes
4answers
8k views

Different Test Set and Training Set Distribution

I am working on a data science competition for which the distribution of my test set is different from the training set. I want to subsample observations from training set which closely resembles test ...
15
votes
2answers
7k views

StandardScaler before and after splitting data

When I was reading about using StandardScaler, most of the recommendations were saying that you should use StandardScaler before ...
6
votes
1answer
4k views

Data preprocessing: Should we normalise images pixel-wise?

Let me present you with a toy example and a reasoning on image normalisation I had: Suppose we have a CNN architecture to classify NxN grayscale images in two categories. Pixel values range from 0 (...
3
votes
1answer
503 views

How to visualize data of a multidimensional dataset (TIMIT)

I've built a neural network for a speech recognition task using the timit dataset. I've extracted features using the perceptual linear prediction (PLP_ method. My features space has 39 dimensions (13 ...
2
votes
1answer
23 views

Image normalisation methods

I have found some research papers specifying explicitly the normalisation technique they used to get the results. What difference do IMG /255.0 And ...
-1
votes
1answer
311 views

What are the best way to handle missing values [closed]

Suppose we have a dataframe df in python, with numerical and categorical variables. For Numerical, when do we replace by mean and when by median. For ...