k-Nearest-Neighbor Classifiers These classifiers are memory-based, and require no model to be fit. Given a query point x0, we find the k training points x(r),r = 1,...,k closest in distance to x0, and then classify using majority vote among the k neighbors.

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K-Nearest Neighbour Classifier accuracy [migrated]

I followed an example of the MATLAB KNN classifier with 10 fold cross validation, I am lost at the stage of computing the model's performance, Please kindly look at my code below and advice on how i ...
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9 views

data treatment before or after train/test sets split?

I have a variable in my data with NA values and I want to apply knn input. Should I do it before or after split the data in train and test set? If I do it after, each set will only use the values in ...
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56 views

What does the k-value stand for in a KNN model?

What is the k-value in a KNN classification model? Is K the number of Clusters?
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9 views

KNN converging to regression function proof (ESL page 19)

In Elements of Statistical Learning, page 19, it says I am confused what it means by "under mild regularity condition" and how one can prove the statement $\hat{f}(x) \rightarrow E(Y|X = x)$ under ...
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10 views

Smoothing of a 2D Empirical Distribution

I have a number of data points $\theta \in \mathbb{R}^2$ with corresponding values $x \in \mathbb{N}$. I am assuming the $x$ are realisations from a distribution $f(X | \theta)$. Given I have a lot ...
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141 views

If Manhattan distance always performs better on a dataset…what does it mean?

I'm analyzing my dataset using kNN. I experimented with various distance functions but Manhattan seems to perform better in terms of lowest RMSE over various values of k. I've read a bit about ...
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39 views

Explanation of formula for median closest point to origin of N samples from unit ball

In Elements of Statistical Learning, a problem is introduced to highlight issues with k-nn in high dimensional spaces. There are $N$ data points that are uniformly distributed in a $p$-dimensional ...
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13 views

Can KNN theoretically be less accurate than pattern averaging?

My task is pattern recognition. I need to classify 2D matrices into an arbitrary number of classes. The question is: For pattern classification, could k nearest neighbours algorithm ever be less ...
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8 views

What is the cost of finding neighbors in eps radius?

Finding neighbors in eps radius a sample point is called region query. There are data structures reduce cost of such queries. These structures are also used to give k-nearest neighbors of given sample ...
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59 views

Naive Bayes Nearest Neighbor (NBNN) implementation problems in MATLAB

I'm currently trying to classify the CIFAR-10 image dataset. I cam across a number of papers praising the the results from a non-parametric approach called Naive Bayes Nearest Neighbors. It uses SIFT ...
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Choosing optimal K for KNN

I performed a 5-fold CV to select the optimal K for KNN. And it seems like the bigger K gets, the smaller the error... Sorry I didn't have a legend, but the different colors represent different ...
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50 views

Distance measure for categorical attributes for k-Nearest Neighbor

For my class project, I am working on the Kaggle competition - Don't get kicked The project is to classify test data as good/bad buy for cars. There are 34 features and the data is highly skewed. I ...
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9 views

Find input image (ID,passport) in imagesDB based on similarity

I would like to decide if image is exists on DB images (pictures of IDs,passport,Stu. card,etc) I thought of KNN alghorithem that will plot the K closest images. Options for distance metric: 1) sum ...
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1answer
47 views

Are there optimization methods for k-NN parameter $k$?

Currently I am just go through from the min to the max, and determine $k$ by the performance. I am wondering if there's optimization approaches for selecting $k$? I am aware of there's question in ...
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26 views

Finding nearest neighbors using Jaccard distance for positive, real-valued vectors

Say we have $x_i, \ldots, x_n \in R ^ D$ with positive, real components and use Jaccard distance $$d(x_i, x_j) = 1 - \frac{\sum_{d = 1}^D\min(x_i^d, x_j^d)}{\sum_{d = 1}^D\max(x_i^d, x_j^d)}$$ to ...
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65 views

How to solve this problem on Curse of Dimensionality problem - Nearest Neighbours

I have started learning classification techniques and trying to solve the problems from the book Introduction to Statistical Learning. While currently working on the which is based on Curse of ...
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270 views

When should I apply feature scaling for my data

I started a discussion with a collague of mine and we started to wonder, when should one apply feature normalization / scaling to the data? Lets say that we have a set of features with some of the ...
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49 views

Binary classification with KNN

I post here because I don't know how to improve the performance of my binary KNN. The problem is that I have 99.8% Specificity and only 82% Sensitivity, but I'd rather have more Sensitivity than ...
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38 views

KNN - does it use centroids?

I'm really confused now having read so many articles on KNN, I can't help but think I'm missing the obvious. Let's say I have persons P1 and P2, P3 are represented with attributes of height, weight ...
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83 views

Is kNN best for classification?

I wanted to know if kNN might produce the best result for classification? Since, it is not model based, it does not loose any detail and compares every training sample to give the prediction. Hence ...
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16 views

Why SVM with RBF is similar to KNN with prototypes search?

I explored similar questions and everything I can see is that both kNN and RBF are non-parametric methods to estimate the density of probability of your data. However, I am not sure if this has ...
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35 views

How to use Similarity Measure in K-nearest neighbor Classification?

I have a similarity measure just like cosine. How can i use that similarity measure in traditional k-nn classification? Please provide some literature review (research papers) details which i should ...
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40 views

Classification tips for a begginer

I'm doing a graduation work that involves applying Classification algorithms in a dataset of matches from Dota 2 (a popular MOBA game). Here's an explanation of the problem: Dota 2 matches are played ...
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Several categories using k-nearest neighbour

Is it possible to have a training data set for the k nearest neighbour with several categories likes 700 and about 10 attributes?
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148 views

Doing low-dimensional KNN on a large dataset

I have a simple two-dimensional dataset with columns X1,X2, and [outcome], and I want to try KNN (probably K around 100 or 1000, though ideally CV would be possible). The problem is that my dataset ...
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43 views

predict category by using K-NN algorithm having text features

I would like to predict the category of the provided data by using K-NN algorithm. Here is an example of the training data set ...
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1answer
37 views

Classifying a set of photos to places

I want to cluster photos and map them to places. As input I have Photos with locations (lat, long) Places - some as (imprecise) bounding boxes, some just as points, maybe others as bounding ...
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35 views

Method to select meaningful features for nearest neighbor classification

i try to perform some k nearest neighbor classification in R. That for i want to select the most meaningful features to deal with the curse of dimensionality. I have already decided to use Mahalanobis ...
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326 views

Does k-NN with k=1 always implies overfitting?

I found somewhere such statement, but on the other hand in some sources I found, that it is ok. What about risk of overfitting while using 1-NN in binary classification problem where explanatory ...
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1answer
127 views

advantage of euclidean distance for classification

Has euclidean distance any advantage in compare to another distance based methods like Manhatan distance or Maximum difference metric?
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280 views

Is KNN a discriminative learning algorithm?

It seems that KNN is a discriminative learning algorithm but I can't seem to find any online sources confirming this. Is KNN a discriminative learning algorithm?
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192 views

How to deal with unbalanced data

I'm doing data analysis with a dataset of 11795 data points (with 88 features). 85% (9973 points) of these data points correspond to data points belonging to class 1, 5% (589 points) belong to class 2 ...
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22 views

sample size to estimate the best k in kNN

I would like to use a kNN classifier. My data set is quite small and include 2 classes having about 200 samples each one. I need to estimate k by using a cross-validation approach. How many samples ...
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1k views

Why would anyone use KNN for regression?

From what I understand, we can only build a regression function that lies within the interval of the training data. For example (only one of the panels is necessary): How would I predict into the ...
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1answer
381 views

Pros of Jeffries Matusita distance

According to some paper I am reading, Jeffries and Matusita distance is commonly used. But I couldn't find much information on it except for the formula below ...
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62 views

Regression: what to do with categorical predictors?

I've got a few categorical predictors (like gender,...) and now I want to build regression models. So I've made the categorical predictors numeric by for example: "female" --> 1 and "male" --> 0. But ...
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56 views

Is this a correct interpretation of k nearest neighbours?

Given this dataset : name1,name2,distance a,b,1 a,c,5 b,c,8 If k=1 is the following correct : ...
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143 views

kozachenko-leonenko entropy estimation

I'm trying to implement the entropy estimation based on the closest neighbour from Kozachenko and Leonenko but I'm facing a problem I can't solve. The idea is to work in a new set ...
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60 views

Is this a valid use case for Euclidean distance?

I have a set of points which is a count of links that users have clicked on : ...
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1answer
30 views

Looking for measurement for nonlinear model

I use KNN regression to train out a model. The model estimates running time of a program based on different inputs, and the output is a single variable, which is time (double type). I want to ...
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37 views

Best way to classify a set through a single feature

I need to classify a single dataset through a numeric value. I added below a simple dataset to explain what I need. Restriction: Category has two values: 1 or ...
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55 views

What criteria are used to compare feature-based classification techniques?

When comparing feature-based classification techniques, what characteristics about the different processes should be considered? I'm comparing different classification techniques to try to figure ...
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118 views

Feature Selection for look alike modeling using k-NN

I have a list of items and various parameters for each items. For each item on my list i need to identify items which are similar to the item from my whole population . I am planning on using K-NN ...
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71 views

All nearest neighbors in high dimensional space

Suppose I have a very large binary matrix representing $n$ customers and the $m$ products they bought, with $n$ and $m$ both rather large (in the order of millions). The matrix is also pretty sparse. ...
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1answer
752 views

How to define the maximum k of the kNN classifier?

I am trying to use kNN classifier to perform some supervised learning. In order to find the best number of 'k' of kNN, I used cross validation. For example, the following codes load some Matlab ...
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212 views

Can the curse of dimensionality be solved by changing the metric tensor?

My (not too deep) understanding of the curse of dimensionality that affects a classification algorithm, such as k-Nearest Neighbor, is that at higher dimensions the 'sparsity' of euclidean space kicks ...
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174 views

How to interpret the number of k in k-nearest-neighbour classifier?

I have done some classification work using a k-nearest-neighbour classifier (kNN). And the classification performance is evaluated using cross-validation method. Some testing code from Matlab Help are ...
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166 views

regression with kNN on dataset with categorical variables

I am trying to train a regression model for dataset with 500k observations and 3 features. The features are categorical and have 50, 50 and 100 levels. Is (generally) kNN appropriate for this kind of ...
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68 views

Using KNN (with contributing weights) to calculate ranking

Sorry about the noob question, we tried looking through the answers but couldn't make sense of it. We are very basic with our math/stat knowledge, so please bear with us if this makes less relevant ...
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38 views

Implementation of prototype selection in application to nearest neighbor classifier

I am looking for an implementation of prototype selection algorithm and it is highly preferable that implementation would be in Python. I am using sikit-learn, but there is none.