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Questions tagged [preprocessing]

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1answer
5k views

How to implement global contrast normalization in python?

I try to implement global contrast normalization in python from Yoshua Bengio's deep learning book. From the book, to get normalized image using global contrast normalization we use this equation $$\...
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0answers
22 views

Calculating unaffected data [closed]

Some data sets values are missing. Missing values are spread along 1.5 standard deviation from the median with distribution mean = 0 & variance = 5. How much data would remain unaffected in %. Why?...
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0answers
35 views

Checking skewness of variables

I follow a tutorial for the current dataset I'm working on. In this tutorial the target variable is check for skewness, and corrected het for by by taking the log transformation. Hereafter, skewness ...
0
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1answer
135 views

LSTM for prediction of next location step - help with standardization

I have a few questions regarding the topic and I hope someone might have experience with any of them. What I am trying to do is train an LSTM network, whose input is a sequence of N steps in a XYZ ...
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0answers
23 views

Specific data formatting techniques for discontiguous time series?

I'm facing a predicting problem for food alerts. The goal is to predict the variables of the most probable alert in the next x days (also any information I could get about future alerts is really ...
1
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1answer
109 views

Encoding multiple observations from the same feature space

My data contains multiple observations of categorical feature.The feature space is medical symptoms, so the data for this feature is like : ['fever','pain','yellow skin' .... ] .The amount of symptoms ...
2
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1answer
24 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
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0answers
94 views

Remove attributes with missing values exceeding a given threshold in WEKA

I imported csv file into WEKA, i have features that have missing value that has missing value percentage of 70% or above, i want to remove these features by weka or also sort that features by missing ...
1
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1answer
229 views

Cleaning data automatically [closed]

Do you use automatic cleaning tools for data? I mean something similar to h2o.ai's auto ml function but applied to preprocessing data. Or do you always clean data 'by hand'.
3
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1answer
227 views

Standard correlation coefficient of various datasets

I understood the correlation coefficient of the first line. But the correlation coefficient of second and third line differ with the first line in figure 1. Why is it so ?. Even the shapes differ for ...
3
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2answers
58 views

Normalising data with multiple methods

When training a neural network, I appreciate that data normalisation helps training. However, is it a good idea to normalise the data in multiple ways. For instance, is it a good idea to apply z-score ...
0
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1answer
3k views

Extract all the data of a particular month from dataset of different years

In a dataset containing temperatures of different years and I want to extract data of particular month from all different years in single liner code what is the syntax? To extract all the data from a ...
1
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2answers
99 views

Can preprocessing the whole population cause data leakage?

Introduction I understand the problem of data leakage that could be caused by the preprocessing step when our training and test sets are just samples of an unknown population. The preprocessing ...
8
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1answer
3k views

Difference between OrdinalEncoder and LabelEncoder

I was going through the official documentation of scikit-learn learn after going through a book on ML and came across the following thing: In the Documentation it is given about ...
1
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0answers
459 views

Clustering bitcoin addresses with k-means - how would one prepare input

I am looking to perform clustering on bitcoin addresses within the blockchain. I have generated a graph structure of the blockchain with a source address, destination address, value of transaction, in-...
7
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1answer
1k views

Extracting individual emails from an email thread

Most of the open source datasets are well formatted i.e each email message is separated well like the enron email dataset. But out in the real world it is highly difficult to separate a top email ...
1
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2answers
125 views

data pre-processing before image classification

I'm working on a machine learning project, Images classification (shape: 100 x 100)-> (vector of 10000), I did some pre-processing before applying decision trees algorithm , I got an accuracy of 55 % ...
4
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3answers
7k views

How to get spike values from a value sequence?

I have pile of vectors where the values could be plotted like this: Now I want to extract the "spike values" (over a certain threshold say 15,000). In this case there is fifteen. How could this be ...
2
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1answer
256 views

How can I measure the similarity between 2 IP addresses? Is there any code to re-use?

I need to measure the similarity of 2 IP addresses. I could not find any sample code in scala or other languages to find the distance between 2 IPs.
0
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1answer
64 views

What is the the cost of combining categorical variables?

I have 2 categorical variables e.g. state and city. Missing are only in city. As opposed to throwing out all observations with missing values for city or throwing out city all together I was ...
0
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1answer
49 views

Does discretization of continuous features also lose information about distance?

During discretization, it "squashes" nearby values into one bin, losing a little bit of information along the way. But doesn't it also lose information about distances of features? For example, if we ...
0
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2answers
114 views

Transformation of categorical variables (binary vs numerical)

When using categorical encoding, I see some authors use arbitrary numerical transformation while others use binary transformation. For example, if I have a feature vector with values A, B and c. The ...
0
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1answer
44 views

Is it correct to use non-target values of test set to engineer new features for train set?

Suppose, I have a dataset with a feature_1 value and a target value. Now, I want to engineer a new feature by creating relative value by subtracting mean from each value. Question: Can I (1) use ...
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0answers
69 views

How to deal with attributes that can vary arbitrarily for each sample?

Let's say we are trying to classify cars into five different categories. For this, we have a lot of samples described by color, brand, model, year of manufacture and so on. For instance, imagine ...
5
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2answers
5k views

Why is input preprocessing in VGG16 in Keras not 1/255.0

I am just trying to use pre-trained vgg16 to make prediction in Keras like this. ...
1
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0answers
180 views

Audio signal signal processing for background noise reduction or removal

I am performing simple audio recognition using tensor-flow to spot key word or hot word detection. The graph takes the microphone input directly and performs "Audio spectrometer --> mfcc's --> and ...
0
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1answer
466 views

pandas: How to impute the categorical column by the nearest neighbors?

I've a categorical column with values such as right('r'), left('l') and straight('s'). I expect these to have a continuum periods in the data and want to impute nans with the most plausible value in ...
0
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1answer
47 views

Missing Values in Classification

I'm working on a classification problem. I'm trying to build a model which can predict if a bank client will get a loan or not. Some of clients have co-borrower and the majority don't. I also have ...
1
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0answers
52 views

Any tool that can help on manually label a time series data please?

i am working with a 10 years weekly financial time series data set, which has the standard format date open high low close volume. i would like to manually label (classify) the data set with label/...
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0answers
78 views

How standardizing and/or log transformation affect prediction result in machine learning models

I recently ran an elastic net model on my data. My predictors are mostly skewed. I found my model perform slightly better when I standardize on log-transformed data than standardizing on original data....
1
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0answers
146 views

Lowercase texts before tokenizing as pre-processing step for alignment

I am pre-processing some texts and I wonder what the best practice is when preparing your texts for word alignment. I don't know how aligners such as fast align and GIZA++ work under the hood, but I ...
1
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0answers
78 views

Transposing a dataframe (time-series)

I'm working on event-forecasting problem for a supermarket, and the data frame I have looks like (sorry for formatting): ...
1
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2answers
169 views

Preprocessing of Sudoku Dataset from Kaggle

Dataset: https://www.kaggle.com/bryanpark/sudoku I would like to create a neural network for this Dataset. Feature: ...
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0answers
34 views

Normalize data with uneven groups?

I have a dataset with 3 independent variables [city, industry, amount] and wish to normalize the amount. But I wish to do it with respect to industry and city. Simply grouping by the city and industry ...
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0answers
13 views

Are there some resources for filters specifically applicable in big data applications? [closed]

Are there some resources for filters specifically applicable in big data applications? Particularly, are there major differences between filter design for other domains and filter design for data ...
0
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2answers
938 views

How to detect phrases from an English sentence.

The question is not about detecting keyphrases. It is about detecting a combination of words makes a valid phrase or not. For example, "John reads New York Times in New York." Here, the phrases ...
1
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0answers
86 views

Input data for this dataset to be feed into keras for training

Suppose I have 3 csv files which forms the dataset for training a machine learning model in Keras. file1.csv ...
0
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2answers
122 views

Basics: What is the correct sequence for preparing simple data for ML?

I'm just getting started with ML and am busy with my first Kaggle competition (the titanic one). I was just wondering what would be the best way to organise the data to avoid redundancy with the ...
0
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1answer
383 views

How to interpret Hashingvectorizer representation?

I cannot really understand the logic behind Hashingvectorizer for text feature extraction. I can follow the logic of Bag of Word or TFiDF where the features are values for all/certain words/N-grams ...
0
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2answers
66 views

What to do if my target variable is column of lists? [closed]

How I can transform my target variable(Y)? As it is list, I cann`t use it for fitting model, because I must use integers for fitting.
3
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1answer
223 views

Normalizing test data

I have a problem in data normalization. I have data for which I need to create an SVM. I will be using the model for real-time predictions. I know that the test tuples should be normalized using the ...
1
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0answers
23 views

Variable TimeStep in Spatio Temporal 3DConvNet

I'm working on a new project on climate data. I suppose my output $Y(H*W*1)$ is a consequence of a given data scenario $X(C=4*T*H*W)$ and an initial state $Y0(H*W*1)$. I've chosen a temporal ...
1
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1answer
93 views

standardize dataset with numerical and dummy features

I have a dataset with both numerical and categorical features (variables), I converted all the categorical variables in dummies, then I split the train and test data. Now I am at the step where I ...
1
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1answer
88 views

Dropping less frequently used categorical data?

I'm new to the datascience field and working on an assignment. I have a dataset with 150K rows with a categorical and numerical data, the target is a boolean. A categorical column consist of quite ...
1
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3answers
71 views

Need help in understanding a small example

Pardon me, I agree the title of the question is not clear. I would like to know the understanding of below steps which are picked from the textbook "Hands on machine learning". ...
0
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1answer
23 views

Computer Vision: Handling dataset(3D data or scan) with different timesteps

I'm planning on training a CNN on CT scans for classification. The problem is CT scans are taken slice by slice, and in a typical scan, there could be more than 200 slices. The number of slices in a ...
1
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1answer
51 views

Why is it important to have sufficient number of instances in your dataset for each stratum?

As per the figure 1, most of the median-income values are clustered around \$20,000-\$50,000, but some median incomes go far beyond \$60,000. I didn't understand the explanation behind why housing['...
1
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1answer
75 views

How to check if audio samples have only noise or are silent?

I have a wav file I want to split into frames in order to feed it into a machine learning model. The problem is that the audio has silence with some noise at some points. My problem is that I do not ...
2
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2answers
2k views

How to scale prediction back after preprocessing

So I'm a newbie to machine learning and am currently using the iris data set. I ran through a quick online tutorial about predicting stock prices and thought I'd try and do the iris one myself. The ...
3
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2answers
322 views

What pre processing should I use on data to feed into a CNN?

I have a dataset of shape 105 x 501 x 266 where 105 is the number of data and 501 x 266 is ...