# Questions tagged [svm]

Support Vector Machines (SVM) are a popular supervised machine learning algorithm that can be used for classification or regression.

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### Plotting SVM hyperplane margin

I'm trying to understand how to plot SVM hyperplane and its margins by this example: https://scikit-learn.org/stable/auto_examples/svm/plot_svm_margin.html And I got stuck at the plotting the ...
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1 vote
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### How can I weight each point in one-class SVM?

I want to give weights to some data points Specifically, these are points related to anomalies (I'm implementing one-class SVM for anomaly detection) Exactly, I want to consider some data points that ...
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### SVMs: where comes the 1 and -1 in hyperplane equations and where is b?

Concering Support Vector Machines (SVM): it is always mentioned that $\textbf{w}^T\textbf{x}_i - b >= 1$, for $\textbf{x}_i$ of class 1 (i.e. $y=1$) and $\textbf{w}^T\textbf{x}_i - b <= -1$, ...
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1 vote
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### Does linear kernel make SVM a linear model?

I have deleloped several SVR models for my case study using the linear kernel, and those models were optimized using the RMSE as criterion. Now Im searching for additional evaluation metrics and it ...
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### what is the effect of initial weights on model training for different algorithms

If I do a model training on a dataset with three different algorithms Logistic Regression (L1), SVM(S1) and a Neural Net(N1). If I train the models again with the same data set and same parameters ...
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1 vote
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### regression with noisy target vairable

How can I approach a regression problem where the input data is not noisy but the target variable is noisy? Are there any regression algorithms that are robust to a noisy target variable? Also, is it ...
392 views

### Should bag of words in training set include test set data when doing text classification?

I'm doing text classification to identify 'attacks' from Wikipedia comments using a simple bag of words model and a linear SVM classifier. Because of class imbalance, I'm using the F1 score as my ...
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### How the Support Vector Machine will perform if the bias b = 0 in the equation of hyperplane?

We have a soft margin linear SVM and the equation is as follows : How the SVM will perform if b = 0, means the hyperplane is passing through the origin ?
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### Non IID variables and SVM Classifier

I am training an SVM model to predict the trend of stock prices (one-day ahead predictions. Classification task). It Had completely slipped from my mind that SVMs assume IID data until I had a ...
81 views

### Linear Learning Machines

I was reading about Linear Learning Machines (LLMs) and learned that it is closely related with SVMs. Would like to know an example of any concrete problems that can be classified by LLM as I couldn't ...
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### What if Training and testing dataset comes from the same source?

I am working on a classification problem in which I have to distinguish between healthy and damaged plates. when I use the combination of k-means clustering and SVM algorithm together with 10-fold ...
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### Get the prediction probability using prediction function

I'm new to SVM models. I took custom SVM classifier from the github. In there standard predict function was overwritten by custom predict function. ...
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1 vote
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### Interpreting one-class SVM

I am new to SVM (one-class) and was practically investigating it. Got some weird result that I can not explain. Let me demonstrate by some small reproducible code and visualization: ...
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### Is it acceptable to use label encoding for nominal categorical data when one hot encoding would create too many features?

I'm working on a short data science project to compare the accuracy of different classification methods. The groups decided to use and compare Random Forest, Naive Bayes and SVM. The dataset we are ...
1 vote
29 views

### Support Vector Classifier and cost C

Applying SVC (Support Vector Classifier) to the 1-d data shown here: What will be the support vectors for the parameter cost C=0 and C=Infinity? As far as I read about SVM and hyper parameter C I ...
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1 vote
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### Why is the optimal C chosen by GridSearchCV so small?

I'm trying to use GridSearchCV to select the optimal C value in this simple SVM problem with non-separable samples. The issue I'm having is that when I run the code the optimal C is chosen to be ...
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1 vote
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### Need help understanding Hard SVM quadratic program equation

This is from the textbook "Understanding Machine Learning" by Shalev-Schwarz p. 169. Can anyone help me understand why the solutions to this optimization problem need to be divided by the ...
31 views

### Steps to fit a Machine learning model for prediction of up and down market movement

I have around 5 years of data of an index containing many features on a daily basis. I want to classify whether the index will move up or down the next trading day (up or down movement is determined ...
1 vote
29 views

### Finding the dual to an optimization problem on an unsupervised dataset [closed]

We consider the unsupervised dataset $x_1,..x_N \in R^d$ and the optimization problem: $$min_w \,\frac{1}{2}{\left\lVert w \right\rVert}^2,$$ subject to constraints:\forall_{i=1}^N: \phi(x_i)^Tw\...
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### Results of quadratic SVM in Matlab are different from the results obtained in Python

I am trying to replicate a quadratic SVM classifier from Matlab to Python, however I am having different results regarding the accuracy. In Matlab the accuracy is 0.8955 meanwhile in Python the ...
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### How important is outcome variable scaling in SVM regression?

Should I scale outcome variable for SVM regression? What is the magnitude of impact of outcome variable scaling in SVM regression?
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### How to decrease $R^2$ value and change it to positive value [closed]

I'm working on a data, and use regression , as you see bellow: from sklearn.svm import SVR regressor = SVR(kernel = 'linear') regressor.fit(trainX,trainY) above ...
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1 vote
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### Machine learning model (neural network or SVM) for unequal feature matrices size

I have feature matrices obtained from visual bags of words model for various dictionary sizes. Example, Nx5, Nx10, …., Nx15000. Where N is the number of samples and 5, 10, …15000 are the visual ...
656 views

### Preprocessing: StandardScaler() Do we really need mean to be zero?

For instance, many elements used in the objective function of a learning algorithm (such as the RBF kernel of Support Vector Machines or the l1 and l2 regularizers of linear models) assume that all ...
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1 vote
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### Bert and SVM classification

I'm trying to understand the concepts in the title and how they fit into the task of binary classification. According to my understanding so far, you can encode text using various feature-extraction ...
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### Understanding Learning Curves

I would like to clarify my understanding of learning curves with two example plots below. I am experimenting with small data sets here between 500 and 1500 samples to clarify my understanding. My ...
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### One-Class classification

I am currently using an one class classification svm and I am trying to boost the classification results by employing more than one svm-occ with varying gamma parameters and combine these decisions ...
1 vote
585 views

### Why does using a standard scalar on my tf idf matrix make it perform better?

I have a TF-IDF matrix transformed on a list of tweets from a data set I am using. I have a pipeline where I initiate a StandardScalar and then next have my SVM with a linear kernel and auto gamma as ...
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### Intuition behind One Class SVM (Scholkopf)

I am trying to understand the intuition behind the idea of finding a hyperplane that separates the training data from the origin in the feature space. Why separation from origin with a hyperplane ...
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1 vote
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### SVM is margin determined by nearest datapoint or nearest datapoints?

I am studying support vector machines and different resources seem to define the margin differently. Some define the margin as 2 times the distance to the nearest datapoint. Others define the margin ...
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### How plot GridSearch results?

I trained an SVM model with GridSearch ...
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### UserWarning: No contour levels were found within the data range

I am running the exact example give in this SVM example of Scikit learn without any modification. I get the following warning. ...
456 views

### How to find the initial hyperplane in a Support Vector Machine (SVM)?

As far as I understand Support Vector machines, we are trying to find the optimal hyperplane, out of all hyperplanes that are equidistant from the support vectors. There are an infinite number of ...
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1 vote
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### Support Vector Machines (SVM) vs Minimum distance between two convex hulls [closed]

Imagine that we have two sets of seperable points, X and Y, in the plane (R^2) that we want to classify. To find the optimal line (hyperplane) that separates these two sets of points we can: Run a ...
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### SVM overfitting with consistent validation results

I have some imbalanced (1400 samples of which 250 are +ve) data for a binary classification problem and I am running an SVM grid search optimising for precision. I am trying 3,4,5,6,7,and 8 stratified ...
1 vote
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The constrained optimization problem in SVM is given by min 1/2 ||w||^2 s.t y(i)(w^T x(i) + b >= 1 for all i Now converting this to an unconstrained optimization problem gives the lagriangian L as ...
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### Why multi-class SVM can't detect some classes?

I use PCA and multi-class SVM for classifying 4-class problem in the Python environment. But in results, I see some differences in detection rate (Unweighted Accuracy in this problem). For example: ...
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### Non semi positive definite kernel matrix

What happens if we run a support vector machine model using a kernel that does not satisfy requirements such as non-positive semi definite? This is my flow of thought: In kernel methods $w.x$ is ...
1 vote
111 views

### SVM - Making sense of distance derivation

I am studying the math behind SVM. The following question is about a small but important detail during the SVM derivation. The question Why the distance between the hyperplane $w*x+b=0$ and data ...
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1 vote
508 views

### SVM on BERT-Embeddings with very small dataset does not converge

I am trying to reproduce the results from this paper where they use a linear SVM on top of BERT-Embeddings for text-classification. They use the average of the token-embeddings which results in a 768 ...
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1 vote
390 views

### How much data do you need to build a classifier?

I would like to ask you what a good size of dataset would be for building a classifier. I know that there are datasets of 1000 obs and datasets of 1m obs. But I also read papers where classifiers were ...
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### Why Imblearn pipeline gives very different results when used scaler and under sampling method swapped

I am using the Kaggle's credit card fraud detection dataset (https://www.kaggle.com/mlg-ulb/creditcardfraud) In order to create a balanced datasets I was testing RandomUnderSampler() and NearMiss(). I ...
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1 vote
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### ValueError: y should be a 1d array, got an array of shape (285, 30) instead [closed]

I am using this data set below and I am trying to find the support vector machine of the data set. Also I have my code and error below as well. http://scikit-learn.org/stable/modules/generated/sklearn....
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### GridSearchCV Acting Weird

I am using GridSearchCV to find the best combination of parameters for SVM. However, the parameters chosen by GridSeasrchCV do not seem to be the best ones. I tried some parameters randomly and they ...
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1 vote
145 views

### Is Recursive Feature Elimination finding best features subset?

On a set of 9 features I have applied Recursive Feature Elimination (RFE) algorithm using SVM estimator, following approach from (1). When requesting a subset of size 1 to be found, then RFE returned ...
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