Questions tagged [machine-learning]

Machine learning algorithms build a model of the training data. The term "machine learning" is vaguely defined; it includes what is also called statistical learning, reinforcement learning, unsupervised learning, etc. ALWAYS ADD A MORE SPECIFIC TAG.

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23 views

timeseries forecasting when datapoints doesn't start at same time period

I have a dataset which has lifecycle information of different products but all the products doesn't start selling in same period or same year/quarter.In this case how should i do time series modelling ...
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1answer
300 views

How well should backpropagation agree with finite difference methods when calculating derivatives of the error function?

I have attempted to write a Neural Network code, and it was suggested in my textbook (Bishop - Pattern Recognition & Machine Learning) that a very useful debugging technique is to check your $\...
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267 views

handling dataset if some columns have sparse data

1)if in a dataset 8 columns and of them 3 columns have sparse data[lots of missing values].can anyone tell me what are the general practices followed to transform this data before modelling. I know we ...
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1answer
26 views

Is this problem Multiclass or MultiLabel?

I am working on a coursework that asks me to take an image and classify it in one of the 15 scenes. An image can be only 1 class at a time. So that makes it a multiclass problem right? How could one ...
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41 views

How to build a model that maps strings to lists of strings?

I have a mapping from strings to rows in a data table. Each strings maps to exactly one row in a table but the opposite is not generally true (one row can be "bound" to different strings. For example ...
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1answer
173 views

Bayes decision rule and thresholding

The best possible classification is for a set of samples drawn from any probability distribution is given by the Bayes decision rule. For any distribution, the rule is given by $f(x) = 1 ~if ~\eta(...
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344 views

The feature space from Gaussian kernel is infinite-dimensional, are there countably or uncountably many basis?

My attempt: Let $x,y\in\mathbb{R}^d$. We already know the Fourier transform of a Gaussian function is a Gaussian function.If substituting $x-y$ for the variable after Fourier transform, we have $$ \...
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232 views

LOOCV v/s K fold Cross validation bias

Why LOOCV(Leave-One-Out Cross-Validation) has less bias than K fold Cross Validation ? Please explain with example if possible
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143 views

Using same data twice in a machine-learning model

I am working on a machine learning problem with 37 features to learn from. So the method I plan on using is as follows: 1) I do a sentiment prediction on 17 of these features to output {negative, ...
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37 views

Are there simple memory-efficient ways to do multi-instance learning?

At the moment, I'm simply using mean of the features in all the instances in a bag to represent a given bag. I've also tried using min/max, gmean and hmean, but didn't get any better results. Are ...
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2answers
43 views

Quantify quality of multi label assignment

I am interested in quantifying how well a multi label assignment performs. E.g. given 3 coloured boxes red, green and blue, with 20 likewise coloured balls in each. A monkey is handed all the balls ...
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1answer
57 views

How to decide if a classifier is linear or not?

If the decision boundary of a binary classifier consists of multiple hyperplanes, is it still a linear classifier? If not, in multi-class classification, how do we define linear classifier? Can we ...
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180 views

My predictors have strong collinearities, yet linear regression performs as good as partial least squares. Why?

I am trying to predict a single response from twelve explanatory variables. There exist strong correlations between my variables. The correlation matrix looks as follows, and the data have a ...
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1answer
748 views

Forward search feature selection and cross-validation

I've a question regarding forward search for feature selection. Basically, I've found here and here that the procedure is the following: As the procedure suggests, the cross-validation is applied ...
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176 views

How do you learn GLove word vectors?

$X_{ik} = \# $ times work $i$ occurs in the context of work $k$. $X_i$ is the number of times word $i$ occurs. $P_{ik} = \frac{X_{ik}}{X_i}$. It's not clear to me what equation 3 solves and why the ...
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1answer
25 views

what does analyzing an algorithm in the stochastic setting mean?

Does stochastic setting for a data mean that the distribution of the data is fixed, and data points are getting generated i.i.d from that distribution? If not, what does it usually mean? Thank you
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120 views

classification on time series data

This is a problem related to classification on a time-ordered sequence of events. I have a data set that consists on a map between two types, A and B, of user identifiers, so that the map is one-to-...
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71 views

Does the Support Vector Machine favor datasets with fewer features?

I am a bit concerned, as there are so many questions asked and so few answers given. I take it, machine learning has become quite common to use, but only little is really understood about their nature....
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2answers
380 views

How does one know if normalizing is improves reconstructions in the task of auto-encoding?

I wanted to understand the performance on an algorithm in the auto-encoding task and compare understand if normalizing the data was a good idea or not and compare the performance when the data is ...
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1answer
90 views

Terminology: Vector, attributes, and matrices in a dataset

I am confused about the terms "vectors", "attributes", and "matrix" when applied to a dataset. I know that attributes are the features or columns of the dataset, and the matrix is $N \times M$ data ...
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304 views

Why is the linear regression coefficients estimated by fitlm function (or regress) in Matlab and mathematical equation different?

I am trying to estimate the linear regression coefficients from mathematical equations. But I get different results using standard function and the mathematical equation which is $\beta=(X^TX)^{-1}X^...
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1answer
206 views

How to measure classifier performance on small and skewed sample dataset?

I have a small sample dataset (n=25) that represents the ground truth for a larger set (n=10k). I am doing a classification task and obtain, say, 3 true positives, 20 true negatives, 1 false positive, ...
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1answer
69 views

How to choose the relative sizes of training and validation sets?

When I work with the methods of data mining, the data is split in training and validations data samples (and sometimes test). I know training + validation = 100%. Which criteria can I use to find a ...
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1answer
246 views

How Neural Networks' prediction in R works on periodic data?

I have a data set x x <- c(1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,6,6,6,6,7,7,7,7) As my entries with a period of 4. And ...
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1answer
236 views

Suggestions for Neural Network Structure for Time-Series prediction with constant covariates

I've been working on a time series prediction problem and wondered if someone has run across a similar problem structure & can make a suggestion on how to structure the training data, network, or ...
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1answer
77 views

Need guidance on image classification problem with large feature matrix

So I've got an interesting problem that I'm struggling with and I wanted to hear some ideas on possible solutions. The data is not public and I can't go into much detail. The problem involves a ...
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901 views

Why is the “training score” I get from the learning curve of Multinomial Naive Bayes so different from the training score of the Bernoulli version?

I'm comparing the learning curves of Bernoulli and Multinomial Naive Bayes using the 20_newsgroups dataset from scikit-learn for text-classification. I considered both the "training score" and the "...
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97 views

Is it acceptable to use class probabilities as weights for a weighted average when the bins are numbers 1 to 5?

I have a Multi Class SVM that can predict what class some observation belongs to. There are 5 classes. They are trained for observation that scored 1 to 5. I want the MC-SVM to predict a class for ...
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1answer
102 views

Neural Network border condition or extrapolation data

I was reading the user guide of NN for Matlab and I found this quote about extrapolation data: It is important that the data cover the range of inputs for which the network will be used. ...
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60 views

Is fitting hyperparameters to data in a Machine Learning model appropriate?

I have constructed a machine learning model (it is similar to Naive Bayes) within the Bayesian framework, and as such, have must select priors. In my brief exposure to Bayesian statistics, I was ...
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138 views

Find the specific hypothesis in binary classification problem

Let $$A+ = \{(1,0), (-1,0), (0,1), (0,-1)\}$$ and $$A- = \{(2,2), (-2,2), (2,-2), (-2,-2)\}$$ represent the positive and negative training instances respectively. The hypothesis space used in this ...
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1answer
151 views

machine learning with asymmetric training data frequencies

I have about a million rows of data being collected every day, and I am trying to predict a government figure which is released on a less frequent basis, about once a month. Compared to a traditional ...
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1answer
35 views

what algorithm is used by google to recognize songs?

I've googled around (which really should be revealing how deep their grip of the world goes :P ) and haven't found any details about the actual algorithm. Just a jumping off point to start researching ...
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1answer
106 views

What is the best method to predict test data once I know the training data and training label

What is the best method to predict test data once I know the training data and training label(continuous variables), so that I can get smallest prediction error.
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261 views

High difference between cv rate and classification accuracy in libsvm

edit: nevermind I solved it I am training an svm on a dataset with 5 classes using libsvm. I have a training set and a test set. I am using the easy.py script. The accuracy is a lot worse than the ...
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277 views

Singular Value Decomposition and Least Squares

From Elements of Statistical Learning (pp. 64, 66), they explain how the $N \times p$ data matrix $X$ can be written as $$X = UDV^{T}$$ Here $U$ and $V$ are $N \times p$ and $p \times p$ orthogonal ...
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76 views

Modeling worker performance parameters for optimum allocation of tasks to workers

Lets say we have an English to French translation task in a company and there are 100s of workers who are proficient in doing this task but each worker has its own unique attributes which allow them ...
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1answer
37 views

I would like to know whether expectation maximization is relevant to cost optimization imbalance

I have a cost matrix which has probability confusion matrix Here is the cost predict good-actually good: 0 predict good-actually bad: 3 consequence points (negative) predict bad-actually bad: 0 ...
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688 views

Accuracy decreased after feature selection

For my machine learning study, I tested different algorithms like SVM, SMO, Naive Bayes, Trees etc. All the algorithms resulted with low accuracy levels. In fact the highest accuracy I obtained was 46%...
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1answer
39 views

Regression analysis terminology

I am running a machine learning algorithm where all of my independent variables are categorical. However, instead of fitting all of my features into the model all at once and getting static co-...
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89 views

Transformation to be used for continuous variable

I have a data set where I am doing a binary classification. I have close to 500 features and 200K observations. Now I also have few continuous variables as features. I don't think just using these ...
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1k views

Cutoff value in linear discriminant analysis with two groups

I have a simple linear discrimininant analysis with two classes. Prior probabilitiest are fixed to 0.5 and number of cases is equal between groups. In this case the cutoff value could be calculated as ...
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66 views

Predict class label at time t given time-series of vectors up to time t

Given a series of $k=4$ vectors (in $\mathbb{R}^n$), with $n=70$ at time $t=-3$, ..., $t=0$, and class labels for vectors at $t=-3$, ..., $t=-1$. Which machine learning approach would be best for ...
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378 views

Estimating number of clusters using Gap Statistics

Since my application is for streaming data, I chose to use BIRCH to create clusters. BIRCH doesn't produce high quality results, therefore it requires "global clustering step" to improve output ...
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1answer
270 views

How to build classification model towards some rare response classes?

I was asked to build a predictive classification model that can predict some types of response. I am interested in 6 classes, however, the total occurence of these 6 classes (out of almost half a ...
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1answer
73 views

Real world model training in R: how to get instant feedback?

I want to train a model. I can just randomly choose method (e.g. random forest), put whole dataset, wait a few hours, check accuracy, plot every possible curve (like accuracy vs train size) and see ...
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1answer
613 views

Motivation behind parameter sharding for Downpour SGD

Why does the Downpour model shard the parameters into separate groups? Is there any advantage of making one cluster responsible for changing only certain parameters?
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1answer
40 views

Dimension reduction: how do we know whether the reduced variables have already captured most information of the original higher-dimensional variables?

I am working on machine learning methods to do dimensional reduction. And I am wondering are there any ways to determine whether the reduced variables have already captured most information of the ...
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1answer
57 views

What is an appropiate machine learning algorithm for my problem?

I was having an idea for a software, which would make use of machine learning, and I started to code it. I got stuck at selecting the algorithm, since I'm not familiar with this field. My use-case is:...
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441 views

R: Is it possible to retrieve a KNN model's predicted Y at a given point?

I've been asked to compare the predicted value of a GLM fit at a specific point to that of a KNN fit at the same point. However I can't find any code or functions to do this with KNN models. Is it ...