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Questions tagged [python]

Use for data science questions related to the programming language Python. Not intended for general coding questions (which should be asked on Stack Overflow).

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73 votes
7 answers

Open source Anomaly Detection in Python

Problem Background: I am working on a project that involves log files similar to those found in the IT monitoring space (to my best understanding of IT space). These log files are time-series data, ...
ximiki's user avatar
  • 933
10 votes
1 answer

Why you shouldn't upsample before cross validation

I have an imbalanced dataset and I am trying different methods to address the data imbalance. I found this article that explains the correct way to cross-validate when oversampling data using SMOTE ...
sums22's user avatar
  • 437
5 votes
3 answers

Obtaining consistent one-hot encoding of train / production data

I'm building an app that will require user input. Currently, on the training set, I run the following code, in which data is a pandas dataframe with a combination ...
Andrew Maurer's user avatar
240 votes
10 answers

What's the difference between fit and fit_transform in scikit-learn models?

I do not understand the difference between the fit and fit_transform methods in scikit-learn. Can anybody explain simply why we ...
Kaggle's user avatar
  • 2,877
3 votes
4 answers

Is it possible to get worse model after optimization?

I am trying recently to optimize models but for some reason, whenever I try to run the optimization the model score in the end is worse than before, so I believe I do something wrong. in order to ...
Reut's user avatar
  • 349
95 votes
10 answers

ValueError: Input contains NaN, infinity or a value too large for dtype('float32')

I got ValueError when predicting test data using a RandomForest model. My code: ...
Edamame's user avatar
  • 2,765
16 votes
1 answer

Multi-dimentional and multivariate Time-Series forecast (RNN/LSTM) Keras

I have been trying to understand how to represent and shape data to make a multidimentional and multivariate time series forecast using Keras (or TensorFlow) but I am still very unclear after reading ...
Bastien's user avatar
  • 263
5 votes
1 answer

How to preprocess with NLP a big dataset for text classification

TL;DR I've never done nlp before and I feel like I'm not doing it in the good way. I'd like to know if I'm really doing things in a bad way since the beginning or ...
gabriel garcia's user avatar
63 votes
9 answers

Tools and protocol for reproducible data science using Python

I am working on a data science project using Python. The project has several stages. Each stage comprises of taking a data set, using Python scripts, auxiliary data, configuration and parameters, and ...
Yuval F's user avatar
  • 761
125 votes
2 answers

Training an RNN with examples of different lengths in Keras

I am trying to get started learning about RNNs and I'm using Keras. I understand the basic premise of vanilla RNN and LSTM layers, but I'm having trouble understanding a certain technical point for ...
Tac-Tics's user avatar
  • 1,370
14 votes
1 answer

How to Predict the future values of time horizon with Keras?

I just built this LSTM neural network with Keras ...
Nbenz's user avatar
  • 283
0 votes
2 answers

What is the state-of-the-art in prediction\classification missing labels in partially labeled data?

Overview Let's say I have the following data: ...
Mario's user avatar
  • 400
150 votes
17 answers

Best python library for neural networks

I'm using Neural Networks to solve different Machine learning problems. I'm using Python and pybrain but this library is almost discontinued. Are there other good alternatives in Python?
55 votes
2 answers

train_test_split() error: Found input variables with inconsistent numbers of samples

Fairly new to Python but building out my first RF model based on some classification data. I've converted all of the labels into int64 numerical data and loaded into X and Y as a numpy array, but I am ...
josh_gray's user avatar
  • 653
12 votes
1 answer

Keras LSTM with 1D time series

I'm learning how to use Keras and I've had reasonable success with my labelled dataset using the examples on Chollet's Deep Learning for Python. The data set is ~1000 Time Series with length 3125 with ...
user1147964's user avatar
10 votes
2 answers

Transform an Autoencoder to a Variational Autoencoder?

I would like to compare the training by an Autoencoder and a variational autoencoder. I have already run the traing using AE. I would like to know if it's possible to transform this AE into a VAE and ...
Kahina's user avatar
  • 634
4 votes
2 answers

Imbalanced Dataset: Train/test split before and after SMOTE

This question is similar but different from my previous one. I have a binary classification task related to customer churn for a bank. The dataset contains 10,000 instances and 11 features. The target ...
KK_o7's user avatar
  • 67
147 votes
13 answers

Why do people prefer Pandas to SQL?

I've been using SQL since 1996, so I may be biased. I've used MySQL and SQLite 3 extensively, but have also used Microsoft SQL Server and Oracle. The vast majority of the operations I've seen done ...
87 votes
6 answers

strings as features in decision tree/random forest

I am doing some problems on an application of decision tree/random forest. I am trying to fit a problem which has numbers as well as strings (such as country name) as features. Now the library, scikit-...
user3001408's user avatar
  • 1,005
41 votes
5 answers

Is it necessary to standardize your data before clustering?

Is it necessary to standardize your data before cluster? In the example from scikit learn about DBSCAN, here they do this in the line: ...
makansij's user avatar
  • 869
21 votes
3 answers

Feature extraction of images in Python

In my class I have to create an application using two classifiers to decide whether an object in an image is an example of phylum porifera (seasponge) or some other object. However, I am completely ...
Jeremy Barnes's user avatar
15 votes
3 answers

Keras Sequential model returns loss 'nan'

I'm implementing a neural network with Keras, but the Sequential model returns nan as loss value. I have sigmoid activation ...
pairon's user avatar
  • 405
14 votes
2 answers

How to train model to predict events 30 minutes prior, from multi-dimensionnal timeseries

Experts in my field are capable of predicting the likelyhood an event (binary spike in yellow) 30 minutes before it occurs. Frequency here is 1 sec, this view represents a few hours worth of data, i ...
William D's user avatar
  • 143
11 votes
2 answers

Is max_depth in scikit the equivalent of pruning in decision trees?

I was analyzing the classifier created using a decision tree. There is a tuning parameter called max_depth in scikit's decision tree. Is this equivalent of pruning a decision tree? If not, how could I ...
Suhail Gupta's user avatar
9 votes
3 answers

Is There a Way to Re-Calibrate Predicted Probabilities After Using Class Weights?

I have classification data with far more negative instances than positive instances. I have used class weights in my models and have achieved the discrimination I want but the predicted probabilities ...
from keras import michael's user avatar
9 votes
1 answer

When does decision tree perform better than the neural network?

I was experimenting with different modelling methods including KNN, Decision Trees, Neural Networks and SVN and trying to fit my data to see which works the best. To my surprise, the decision tree ...
Suhail Gupta's user avatar
6 votes
1 answer

Correlation between specific columns of a data set

I have a CSV file which has 150 columns belonging to 7 categories but I want a correlation between 2 categories. The categories are movies and music, 12 and 19 columns respectively. Is there a way ...
Maha Kamal's user avatar
6 votes
2 answers

Python or R for implementing machine learning algorithms for fraud detection [closed]

I was wondering which language can I use: R or Python, for my internship in fraud detection in an online banking system: I have to build machine learning algorithms (NN, etc.) that predict transaction ...
Hamza's user avatar
  • 61
2 votes
4 answers

Best methods to solve class imbalance problem and why?

I have a data set where I need to detect fraud. 99% are not fraud and 1% are. What methods can be used to solve problems where classes are imbalanced?
John Constantine's user avatar
2 votes
1 answer

String handling by OneHotEncoder

I am reading everywhere on new questions and blogs that since version 0.20, OneHotEncoder is able to handle string features. Moreover, the documentation is what looks more ambiguous. Here are the ...
pragun's user avatar
  • 171
1 vote
1 answer

what kind of algorithm should I use to classify the text data example given?

What kind of classification or learning algorithm that suits this kind of data example If I have to build a model using the given key words then predict column B and then to column A? what kind of ...
User123456's user avatar
1 vote
4 answers

Exceptionally high accuracy with Random Forest, is it possible?

I need your help to find a flaw in my model, since it's accuracy (95%) is not realistic. I'm working on a classification problem using Randomforest, with around 2500 positive case and 15000 negative ...
Francesco Ambrosini's user avatar
61 votes
4 answers

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 ...
Saurabh Singh's user avatar
46 votes
5 answers

How to force weights to be non-negative in Linear regression

I am using a standard linear regression using scikit-learn in python. However, I would like to force the weights to be all non-negative for every feature. is there any way I can accomplish that? I was ...
user's user avatar
  • 2,003
46 votes
2 answers

Merging two different models in Keras

I am trying to merge two Keras models into a single model and I am unable to accomplish this. For example in the attached Figure, I would like to fetch the middle layer $A2$ of dimension 8, and use ...
Rkz's user avatar
  • 1,033
33 votes
3 answers

Hypertuning XGBoost parameters

XGBoost have been doing a great job, when it comes to dealing with both categorical and continuous dependant variables. But, how do I select the optimized parameters for an XGBoost problem? This is ...
Dawny33's user avatar
  • 8,296
24 votes
4 answers

Looking for a good package for anomaly detection in time series

Is there a comprehensive open source package (preferably in python or R) that can be used for anomaly detection in time series? There is a one class SVM package in scikit-learn but it is not for the ...
pythinker's user avatar
  • 1,267
21 votes
4 answers

Train, test split of unbalanced dataset classification

I have a model that does binary classification. My dataset is highly unbalanced, so I thought that I should balance it by undersampling before I train the model. So balance the dataset and then ...
lads's user avatar
  • 413
20 votes
5 answers

Python library to implement Hidden Markov Models

What stable Python library can I use to implement Hidden Markov Models? I need it to be reasonably well documented, because I've never really used this model before. Alternatively, is there a more ...
neural-nut's user avatar
  • 1,783
20 votes
5 answers

Do modern R and/or Python libraries make SQL obsolete?

I work in an office where SQL Server is the backbone of everything we do, from data processing to cleaning to munging. My colleague specializes in writing complex functions and stored procedures to ...
AffableAmbler's user avatar
17 votes
2 answers

Recommending movies with additional features using collaborative filtering

I am trying to build a recommendation system using collaborative filtering. I have the usual [user, movie, rating] information. I would like to incorporate an ...
Sidhha's user avatar
  • 397
14 votes
2 answers

Preprocessing for Text Classification in Transformer Models (BERT variants)

This might be silly to ask, but I am wondering if one should carry out the conventional text preprocessing steps for training one of the transformer models? I remember for training a Word2Vec or Glove,...
TwinPenguins's user avatar
  • 4,279
13 votes
2 answers

Perform k-means clustering over multiple columns

I am trying to perform k-means clustering on multiple columns. My data set is composed of 4 numerical columns and 1 categorical column. I already researched previous questions but the answers are not ...
Lola's user avatar
  • 141
13 votes
2 answers

Activation function between LSTM layers

I'm aware the LSTM cell uses both sigmoid and tanh activation functions internally, however when creating a stacked LSTM architecture does it make sense to pass their outputs through an activation ...
lsfischer's user avatar
  • 242
12 votes
4 answers

Neural networks - Find most similar images

I am working with Python, scikit-learn and keras. I have 3000 thousands images of front-faced watches like the following ones: Watch_1, Watch_2, Watch_3. I want to write a program which receives as ...
Outcast's user avatar
  • 1,057
12 votes
3 answers

Help regarding NER in NLTK

I have been working in NLTK for a while using Python. The problem I am facing is that their is no help available on training NER in NLTK with my custom data. They have used MaxEnt and trained it on ...
Sarmad's user avatar
  • 295
11 votes
1 answer

Multiple Categorical values for a single feature how to convert them to binary using python

I have a data set of movies which has 28 columns. One of them is genres. For each row in this data set, the value for column genres is of the form "Action|Animation|Comedy|Family|Fantasy". I want to ...
aks_Nin's user avatar
  • 111
11 votes
6 answers

Python: Handling imbalance Classes in python Machine Learning

I have a dataset for which I am trying to predict target variables. ...
SRS's user avatar
  • 1,065
10 votes
2 answers

Using Cross Validation technique for a CNN model

I am working on a CNN model. As always, I used batches with epochs to train my model. When it completed training and validation, finally I used a test set to measure the model performance and generate ...
Hunar's user avatar
  • 1,147
10 votes
2 answers

Why `max_features=n_features` does not make the Random Forest independent of number of trees?

Consider the following simple classification problem (Python, scikit-learn) ...
Jorge Leitao's user avatar

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