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training (or estimation) of statistical models or algorithms.

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feature selection and classification - train and test on the sample?

I have a dataset of 93 records and 45 radiomics variables from various CT scans. I wanted to check if age and sex could be classified by the variables so I made a new variable with both sex and age. I ...
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How to generate train / test data for a classifier with only simulated feature data?

We are working on a binary classification problem for which real world data is extremely rare. We are using an HMM model for performing classification, and the feature data is derived from simulating ...
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8 views

What a convex Precision-Recall curve means for training dataset?

Situation I have trained a GBDT model(gradient-boosted decision tree, a tree ensemble model) with a training dataset, and when I calculate PR curve on the same training set, it looks convex: For ...
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16 views

GAN training: Both G and D has very low loss

I am training a GAN. At the beginning the generator has a very high loss, which converges over time. After some time, the image quality seems pretty good, but both the generator and discriminator have ...
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12 views

How to train a NN with multiple outputs when not all of them are known in a test set?

I am working on a boundary value problem. So far I am using the implementation from the following paper Aarts, L.P. & van der Veer, P. Neural Processing Letters (2001) 14: 261. https://doi.org/10....
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1answer
15 views

Should the distribution of my samples in my model be equal to to the original data set?

In my original data set I see a distribution of 70% belongs to label A and 30% belongs to label B. For my train, validation and test set I maintained the same ratio. However, I wonder whether this is ...
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16 views

How to implement the Walk-Forward optimization for RNN

Say you have 24 time steps in total, and you are trying to fit an RNN model. You designate the most recent 5 terms as test period, and the others as train period. In the training process, you start ...
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1answer
24 views

Standardization on training only or also including testing data?

My question is very much related to this one: How to apply standardization/normalization to train- and testset if prediction is the goal? However, my testing data is not a single observation that I ...
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36 views

How to Split Time Series Data to train/test for RNN [duplicate]

Let's say I have a set of time series data with 32 time steps. My goal is to predict what the data value would be for the next time step, given data for 30 previous time steps. Would it be okay to ...
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12 views

I am trying to build a progressive auto encoder neural network and I am not sure how to discard old weights?

The goal of the network is simple, encode and decode images at a smaller scale and slowly increasing the network complexity, the input image size and its output quality. My current weights for my ...
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23 views

Accuracy varying considerably depending on selection of test/train set

I have a large database that is being used for a classification problem. The original total database is being partitioned 80% into sample 1 (where 80% is for training and 20% for validation) and 20% ...
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10 views

Training Gaussian Restricted Boltzmann Machines with Noisy Rectified (nrelu or ssu) linear hidden units

I'm not sure how to implement this architecture. I'm following this thesis http://www.cs.toronto.edu/~ndjaitly/Jaitly_Navdeep_201411_PhD_thesis.pdf (pag 17-19) or this paper http://www.cs.toronto.edu/~...
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11 views

different between effect of episodes and time in DQN and where is the updating the experience replay

In DQN paper of DeepMind company, there are two loops one for episodes and one for running time in each step (one for training and one for different time-step of running). Am I right? Since, nothing ...
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1answer
48 views

Bootstrapping accuracy, f1-score?

I have typical train/test setting, with an ordinary dataset. As I am comparing performance of two approaches to a problem (namely churn prediction with AdaBoost and ...
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1answer
46 views

In which scenarios are the in-sample error and training error NOT the same?

In Elements of Statistical Learning, Chapter 7 (pages 228-229), the authors define the optimism of the training error rate as: $$ op\equiv Err_{in}-\overline{err} $$ With the training error $\...
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0answers
40 views

When to stop training of neural network when validation loss is still decreasing but gap with training loss is increasing?

During training of CNNs, I often come across this case for training and validation loss : X axis is epochs, Y axis is cross entropy loss. I would like to keep the "best model", meaning the one which ...
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1answer
37 views

Can a ConvNet see patterns that a human cannot?

I am training a ConvNet to detect different types of stripes in my images. As I am working on astronomical images, my pixel values are flux densities and therefore represent ground truth data. When I ...
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1answer
25 views

Interpretation of logistic regression with normalized features

With logistic regression, a one unit change in $X_1$ is associated with a $\beta_1$ change in the log odds of 'success' (alternatively, an $\exp(\beta_1)$-fold change in the odds), all else being ...
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2answers
55 views

Is there a way to incorporate new data into an already trained neural network without retraining on all my data in Keras?

I have already trained a neural network on my data. In the future, I will receive some more data. How can I incorporate this data into my model without rebuilding it from scratch?
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3answers
115 views

When is there a difference between a normal likelihood loss and a least squares loss?

My understanding is that if the errors follow a normal distribution, then using a maximum likelihood loss or a least squares loss to train a model amounts to the same thing. However, I am looking at ...
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0answers
105 views

train / validation / test split

I understand that you typically use three different data sets (train/validation/test) to acquire an unbiased estimate of the performance measurement, because the models are tuned to fit for the train ...
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1answer
139 views

When predicting (not training) using neural networks, why would we have to specify a number of epochs?

I'm looking at code from a Google course on how to use Tensorflow. When explaining how to specify the function for generating predictions from an already trained model, the function they define takes ...
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1answer
30 views

Is it OK to use the parameters for the lowest cost? [duplicate]

In a Neural Network training, the cost of the model changes throughout the training process when using gradient descent (or something analogous), this is the point of the algorithm. However the cost ...
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1answer
33 views

Is it recommended to train a SVM model with the same dataset used for pre-train an autoencoder?

I have a very limited dataset and have used 80% of it to pre-train an autoencoder. Now, I attached the enconder part to a SVM. In order to train the SVM, is ok to train it using the exactly same (80%)...
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1answer
30 views

Dataset requirement for Deep Learning

I am doing research on deep neural networks for prediction. I wanted to know what minimum size of dataset is required for training a deep network. Is there any limitation imposed on how much ...
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2answers
74 views

Difference between train/test and train/validate/test split?

I know this question has been asked here before, but after reading the answers I still dont get the difference. Consider for instance a lasso penalized linnear regression model.This model has a ...
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0answers
16 views

How should Training Data for Fully ConvNets look like?

I've been working with CNNs recently. For a new task, I need to predict objects in an image pixelwise. Fully ConvNets seem to be the way to go. I read the original paper (Long et al., 2014) and a few ...
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1answer
134 views

Why would somebody use a hash function for creating a test/train split instead of random seed?

I'm going through some ML training material from Google (I can't post a link because I'm getting the material through my company). In the part about how to extract data and split it into train and ...
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2answers
38 views

Imputing the mean value from the 'train set' into the 'test set'

I have looked at a couple questions and answers similar to this, the recommendation seems to be the imputation of mean values from the 'training set' into my 'test set'. However, what I am trying to ...
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0answers
80 views

Caret and glmnet giving different lambda and coefficient values

I need to match lambda and coefficient values from cv.glmnet and caret train functions. It is evident from below that both ...
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0answers
22 views

Is there an official rule, or a generally accepted one, for how closely your validation data should match your training data?

I'm finding myself making a gut-feeling judgment more and more often on whether the validation of my model is "close enough" to the modeled results from my training data. I don't recall having ever ...
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33 views

Will indexes change in predictions when using sklearn cross validator?

I am using a Random Forest classifier in sklearn to do binary predictions regarding some locations in a map. In my dataset there is less number of positive data is available. Therefore, even it does ...
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119 views

Creating training and validation sets for churn model

I need to determine a statistically sound methodology for creating training and validation datasets for a churn model. Testing sets and model selection aren't a problem. The data spans 4 years of ...
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22 views

building pairs for wors2vec training

As a training example in word2vec model with negative sampling we use positive pair "context word" - "target word". And add to it k negative samples. Is it true we can use in one training step few ...
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1answer
55 views

How to encourage certain activations during training of neural networks?

Is it possible to train neural networks such that certain activations are rewarded and some other activations are penalized? In other words, I would like the network to generate preferred values more ...
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1answer
367 views

What % is the best train/test split for Time Series Data?

What % is the best train/test split for Time Series Data? Do you think it is still 70/30 ? I am talking about leaving a whole continuous period (in the beginning or in the end) for TEST. I have ...
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1answer
38 views

Some weights in CNN remain constant

When training my CNN, I notice that after several SGD updates, some weights of the layers do not change any more. Is this a normal situation? Will all the weights of the network layers change during ...
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0answers
44 views

Use LOOCV selection function for repeatedcv in caret train

Is there a way to use the LOOCV selection function (combine all of the hold-out predictions) instead of the typical repeatedcv selection function (take the average of the hold-out predictions on each ...
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1answer
290 views

How can the AIC or BIC be used instead of the train/test split?

I've recently come across several "informal" sources that indicate that in some circumstances, if we use the AIC or BIC to train a time series model, we don't need to split the data into test and ...
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45 views

What is difference between training examples generated by continuous bag of words(CBOW) and skip-gram?

This is a simple question that is hard for me: Let's consider simple sentence A B C D and create training examples for skip-gram training (x, y) with number of ...
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73 views

How should scaling be performed for data with empty or negative values for SVM?

I am using LIBSVM. I have some data columns where sometimes the value is either not known or not applicable. In such cases, it could not be calculated even if all the variables are available, but ...
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1answer
202 views

Test and Training dataset correlation while Splitting the dataset

I want to split my main dataset in two part, training dataset and test dataset. In the past i read somewhere (which unfortunately i could not find exactly where was that), that when splitting my ...
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1answer
55 views

Why steep loss reduction is an indication of inadequate initial weight allocation in neural network training?

This article says At times, you might see that your loss drops steeply after a short period of training, before stabilizing. This is a strong indication that your initial weight allocation is ...
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1answer
25 views

Duplicates in feature matrix

I have several points which appear duplicates in the feature matrix (same values for the features). These points may have different values of the target variable. What is the appropriate way to handle ...
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0answers
33 views

When forecasting time series, how does one incorporate the test data back into the model after training?

When you build a classification or regression model, you typically split the data into a train data set and a test data set. The test data is a randomly selected subset of the overall data. Once you ...
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0answers
149 views

How to not overlook rare but important features when preventing over-fitting in a decision tree?

I have a data set where some binary features divide the sample space roughly in half, whereas other features are much less frequent and occur only for 0.0001 - 0.01 of the sample space. However, those ...
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2answers
28 views

How to know the predicted values on training data

How to know the predicted values of the model on training data? I just see the standard metrics such as RMSE and R-squared after run train () function.
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1answer
13 views

What images to train on when discriminating against a certain class

I am building an image classifier that discriminates against a certain class. As a toy example, let's say the classifier checks if the image is a hotdog or not (1 or 0). My question is what images ...
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23 views

RSS and $R^2$ are not suitable for selecting the best model, why? [duplicate]

This is in continuation to question Are RSS and R^2 related to training error only? In section 6.1.3 Choosing the Optimal Model of An Introduction to Statistical ...
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2answers
197 views

What is the cause of the sudden drop in error rate you often see when training a CNN

I've noticed in different papers that after a certain number of epochs there sometimes is a sudden drop in error rate when training a CNN. This example is taken from the "Densely Connected ...