Questions tagged [python]

Use for data science questions related to the programming language Python. Not intended for general coding questions (-> stackoverflow).

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228 votes
10 answers
322k views

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 ...
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  • 2,747
181 votes
1 answer
222k views

Difference between isna() and isnull() in pandas

I have been using pandas for quite some time. But, I don't understand what's the difference between isna() and isnull(). And, ...
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150 votes
17 answers
125k views

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?
134 votes
12 answers
86k views

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 ...
124 votes
14 answers
118k views

Python vs R for machine learning

I'm just starting to develop a machine learning application for academic purposes. I'm currently using R and training myself in it. However, in a lot of places, I have seen people using Python. What ...
112 votes
12 answers
130k views

SVM using scikit learn runs endlessly and never completes execution

I am trying to run SVR using scikit-learn (python) on a training dataset that has 595605 rows and 5 columns (features) while the test dataset has 397070 rows. The data has been pre-processed and ...
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  • 3,795
111 votes
2 answers
102k views

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 ...
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  • 1,230
90 votes
10 answers
382k views

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: ...
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  • 2,485
82 votes
6 answers
131k views

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-...
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72 votes
7 answers
82k views

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, ...
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  • 933
63 votes
8 answers
149k views

How to clone Python working environment on another machine?

I developed a machine learning model with Python (Anaconda + Flask) on my workstation and all goes well. Later, I tried to ship this program onto another machine where of course I tried to set up the ...
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  • 7,917
63 votes
9 answers
94k views

Clustering geo location coordinates (lat,long pairs)

What is the right approach and clustering algorithm for geolocation clustering? I'm using the following code to cluster geolocation coordinates: ...
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  • 773
62 votes
9 answers
10k views

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 ...
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  • 751
58 votes
4 answers
122k views

What is the use of torch.no_grad in pytorch?

I am new to pytorch and started with this github code. I do not understand the comment in line 60-61 in the code ...
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  • 1,137
58 votes
5 answers
52k views

Neural networks: which cost function to use?

I am using TensorFlow for experiments mainly with neural networks. Although I have done quite some experiments (XOR-Problem, MNIST, some Regression stuff, ...) now, I struggle with choosing the "...
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  • 703
50 votes
2 answers
348k views

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 ...
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  • 503
45 votes
5 answers
96k views

Opening a 20GB file for analysis with pandas

I am currently trying to open a file with pandas and python for machine learning purposes it would be ideal for me to have them all in a DataFrame. Now The file is 18GB large and my RAM is 32 GB but I ...
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45 votes
3 answers
31k 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 ...
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44 votes
5 answers
40k views

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 ...
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  • 1,851
43 votes
2 answers
68k views

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 ...
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  • 973
42 votes
4 answers
55k views

Multi GPU in Keras

How we can program in the Keras library (or TensorFlow) to partition training on multiple GPUs? Let's say that you are in an Amazon ec2 instance that has 8 GPUs and you would like to use all of them ...
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40 votes
6 answers
82k views

Calculating KL Divergence in Python

I am rather new to this and can't say I have a complete understanding of the theoretical concepts behind this. I am trying to calculate the KL Divergence between several lists of points in Python. I ...
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  • 703
37 votes
3 answers
192k views

Calculation and Visualization of Correlation Matrix with Pandas

I have a pandas data frame with several entries, and I want to calculate the correlation between the income of some type of stores. There are a number of stores with income data, classification of ...
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  • 525
36 votes
5 answers
25k views

Best practices to store Python machine learning models

What are the best practices to save, store, and share machine learning models? In Python, we generally store the binary representation of the model, using pickle or joblib. Models, in my case, can be ...
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34 votes
5 answers
55k views

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: ...
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  • 791
34 votes
1 answer
67k views

What is the best Keras model for multi-class classification?

I am working on research, where need to classify one of three event WINNER=(win, draw, lose) ...
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33 votes
6 answers
81k views

Sentence similarity prediction

I'm looking to solve the following problem: I have a set of sentences as my dataset, and I want to be able to type a new sentence, and find the sentence that the new one is the most similar to in the ...
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  • 1,248
33 votes
1 answer
29k views

What does from_logits=True do in SparseCategoricalcrossEntropy loss function?

In the documentation it has been mentioned that y_pred needs to be in the range of [-inf to inf] when from_logits=True. I truly ...
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32 votes
6 answers
156k views

Merging multiple data frames row-wise in PySpark

I have 10 data frames pyspark.sql.dataframe.DataFrame, obtained from randomSplit as ...
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32 votes
3 answers
43k views

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 ...
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  • 8,016
32 votes
1 answer
24k views

Ways to deal with longitude/latitude feature [closed]

I am working on a fictional dataset with 25 features. Two of the features are latitude and longitude of a place and others are pH values, elevation, windSpeed etc with varying ranges. I can perform ...
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30 votes
8 answers
148k views

How to count the number of missing values in each row in Pandas dataframe?

How can I get the number of missing value in each row in Pandas dataframe. I would like to split dataframe to different dataframes which have same number of missing values in each row. Any suggestion?...
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  • 2,747
29 votes
6 answers
18k views

What is the reason behind taking log transformation of few continuous variables?

I have been doing a classification problem and I have read many people's code and tutorials. One thing I've noticed is that many people take np.log or ...
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  • 581
28 votes
2 answers
42k views

How to calculate the fold number (k-fold) in cross validation?

I am confused about how I choose the number of folds (in k-fold CV) when I apply cross validation to check the model. Is it dependent on data size or other parameters?
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28 votes
4 answers
45k views

Scikit-learn: Getting SGDClassifier to predict as well as a Logistic Regression

A way to train a Logistic Regression is by using stochastic gradient descent, which scikit-learn offers an interface to. What I would like to do is take a scikit-learn's SGDClassifier and have it ...
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  • 655
28 votes
4 answers
52k views

How to use LeakyRelu as activation function in sequence DNN in keras?When it perfoms better than Relu?

How do you use LeakyRelu as an activation function in sequence DNN in keras? If I want to write something similar to: ...
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  • 1,526
27 votes
4 answers
24k views

Is pandas now faster than data.table?

Here is the GitHub link to the most recent data.table benchmark. The data.table benchmarks has not been updated since 2014. I ...
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  • 580
27 votes
5 answers
17k views

What is the benefit of splitting tfrecord file into shards?

I'm working on speech recognition with Tensorflow and plan to train LSTM NN with massive waves dataset. Because of the performance gains, I plan to use tfrecords. There are several examples on ...
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  • 271
27 votes
5 answers
3k views

VM image for data science projects

As there are numerous tools available for data science tasks, and it's cumbersome to install everything and build up a perfect system. Is there a Linux/Mac OS image with Python, R and other open-...
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  • 411
27 votes
6 answers
3k views

Machine learning techniques for estimating users' age based on Facebook sites they like

I have a database from my Facebook application and I am trying to use machine learning to estimate users' age based on what Facebook sites they like. There are three crucial characteristics of my ...
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27 votes
2 answers
12k views

Keras vs. tf.keras

I'm a bit confused in choosing between Keras (keras-team/keras) and tf.keras (tensorflow/tensorflow/python/keras/) for my new research project. There is a debate that Keras isn't owned by anyone, so ...
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  • 1,165
27 votes
4 answers
18k views

Is there a straightforward way to run pandas.DataFrame.isin in parallel?

I have a modeling and scoring program that makes heavy use of the DataFrame.isin function of pandas, searching through lists of facebook "like" records of ...
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26 votes
3 answers
90k views

How to sum values grouped by two columns in pandas

I have a Pandas DataFrame like this: ...
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  • 523
26 votes
4 answers
13k views

Word2Vec for Named Entity Recognition

I'm looking to use google's word2vec implementation to build a named entity recognition system. I've heard that recursive neural nets with back propagation through structure are well suited for named ...
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  • 2,009
26 votes
1 answer
10k views

PyTorch vs. Tensorflow Fold

Both PyTorch and Tensorflow Fold are deep learning frameworks meant to deal with situations where the input data has non-uniform length or dimensions (that is, situations where dynamic graphs are ...
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  • 15.4k
25 votes
7 answers
7k views

Is Python a viable language to do statistical analysis in?

I originally came from R, but Python seems to be the more common language these days. Ideally, I would do all my coding in Python as the syntax is easier and I've had more real life experience using ...
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  • 478
25 votes
3 answers
45k views

Keras Callback example for saving a model after every epoch?

Can someone please post a straightforward example of Keras using a callback to save a model after every epoch? I can find examples of saving weights, but I want to be able to save a completely ...
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25 votes
5 answers
17k views

Improve the speed of t-sne implementation in python for huge data

I would like to do dimensionality reduction on nearly 1 million vectors each with 200 dimensions(doc2vec). I am using TSNE ...
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  • 1,924
25 votes
4 answers
31k views

Gradients for bias terms in backpropagation

I was trying to implement neural network from scratch to understand the maths behind it. My problem is completely related to backpropagation when we take derivative with respect to bias) and I ...
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  • 385
24 votes
10 answers
124k views

GraphViz not working when imported inside PydotPlus (`GraphViz's executables not found`)

I've been trying to make these packages work for quite some time now but with no success. Basically the error is: GraphViz's Executables not found EDIT: I had ...
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