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8
votes
1answer
132 views

Open-sourced pairwise learning models

I am solving a classification problem using pairwise-learning training set. We have 2 classes: bad and good. We also have pairs of objects $(a_i,b_i)_{i=1}^n$, meaning that object $a_i$ is better than ...
4
votes
1answer
1k views

Out of sample predictions for logistic regression models in R

I have a problem of the form "what is the probability that a user will 'like' a certain movie?" For a bunch of users, I know the movies each has watched historically, and the movies each has liked. ...
9
votes
1answer
1k views

Seasonally adjusted month-to-month growth with underlying weekly seasonality

As a side hobby, I have been exploring forecasting time series (in particular, using R). For my data, I have the number of visits per day, for every day going back almost 4 years. In this data there ...
2
votes
1answer
2k views

How to find best split in decision trees using label vectors?

In single label learning, we have a single label that we need to predict. Most training tasks are single label, like the most common example where we need to predict if a customer is going to be good ...
12
votes
2answers
3k views

Cross validation and ordinal logistic regression

I am trying to understand cross-validation for ordinal logistic regression. The aim of the game is to validate the model used in an analysis... I first construct a toy data set: ...
10
votes
2answers
7k views

How do I improve my neural network stability?

I'm using the neuralnet in R to build a NN with 14 inputs and one output. I build/train the network several times using the same input training data and the same network architecture/settings. ...
10
votes
2answers
26k views

How to perform post-hoc comparison on interaction term with mixed-effects model?

I’m working on a data set in order to evaluate the impact of drying on sediment microbial activities. The objective is to determine if the impact of drying varies among sediment types and/or depth ...
2
votes
2answers
2k views

Convex vs. concave curve - measurement or index

I am interested in a measurement or index that will tell me if a curve is more convex or concave versus a straight line. This curve is sampled in n points and I know the x and y coordinates of these ...
2
votes
2answers
216 views

Intersubject concordance for ratings vs rankings

In my system I ask $n$ people to rate [1,5] $m$ objects (e.g. films). I'd like to get a measure of the inter-subject concordance, i.e. how much the users agreed overall, not just on a particular ...
1
vote
3answers
410 views

learn R (Statistics) [closed]

I'm considering using R for my master thesis in order to do some analyses with the mvpart package. The problem is that I only have limited time to learn the program and to do the analyses. I already ...
5
votes
0answers
470 views

Number of states and symbols in multi class Hidden Markov Model classifier

I'm designing a multi class classifier (for 4 classes) using Discrete HMMs with States N and Symbols M for each of the HMM. However, I found that recognition performance(i.e highest log likelihood) ...
2
votes
4answers
891 views

Network graph with avatars as nodes

I've got a problem. I need to create network graph where avatars are nodes (different sizes). Similar to this one: Furthermore on this image every avatar has the same size, what I need to do is ...
33
votes
3answers
5k views

What is the most accurate way of determining an object's color?

I have written a computer program that can detect coins in a static image (.jpeg, .png, etc.) using some standard techniques for computer vision (Gaussian Blur, thresholding, Hough-Transform etc.). ...
6
votes
1answer
4k views

Cohen's d for 2x2 interaction

I have a significant 2x2 interaction in a between-subjects design. I would normally report omega-squared as my effect-size measure, but I've been asked to provide Cohen's d instead? Can Cohen's d be ...
1
vote
3answers
1k views

Train NN or SVM to classify stock signals

I am applying Neural network and SVM to predict buy-hold - sell signals. I have trained nn and SVM in R. I used nnet function to train NN and svm to train SVM. I provided 20,000 data points to train ...
1
vote
2answers
345 views

Measuring inter-subject agreement in user ratings

In my system I have users rating objects (e.g. films) from 1 to 5 stars. The mean rating clearly tells something about the overall opinion on an object, but I'd like to use a more precise measure of ...
0
votes
0answers
237 views

Posterior mean of exponential functions: how to do it with MCMC?

I am struggling with estimation of posterior mean of simple exponential function f(x)=exp(x). Mixing of the chain is quite good and there is no problem with estimation of simple mean, but since ...
6
votes
1answer
2k views

Incremental training of Neural Networks

Is it valid to train a neural network over and over again with new arriving data (including pruning after each new training)? I plan to collect data for a period of time, train/cv/test the networ, ...
-2
votes
3answers
438 views

Find a mapping of two probability mass function to another probability mass function

Lets' $p$ and $q$ are probability mass functions of two discrete random variables. I need examples of functions $F(p,q)$ that $r = F(p,q)$ and $r$ is a probability mass function for some random ...
2
votes
1answer
897 views

Expected hitting time of a level $a$ for Brownian motion

Let $\{W_t,t \geq 0\}$ be a standard Brownian motion under $\mathbb P$. Let $T_a$ be the hitting time of level $a$, that is: $$T_a= \text{inf}\{t \geq 0:W_t=a\}.$$ From a proposition, we know that $$\...
0
votes
1answer
823 views

Scatter plot of interaction

Is drawing a scatter plot, with fitted regression lines for subgroups, the way to graph a possible interaction in SPSS? I may be missing something but I could not find a specific way to do it. I have ...
5
votes
2answers
361 views

Are all attributes/data points inherently nominal?

I'm trying to design a statistics package in .NET, and I'd like to apply object-oriented design principles to some of the data structures that I'm developing. As I look through sample data sets for ...
7
votes
2answers
322 views

Comparing a sample distribution to an implied distribution

I have a task that is specific to inventory management that is currently driving me crazy. To summarize the problem: We regularly must monitor inventory settings to ensure that they represent true ...
2
votes
1answer
159 views

Join parameter estimation is always better than independent parameter estimation. True?

I have the vague recollection of a result that states something along the lines of Joint parameter estimates always lead to smaller variance than independent parameter estimates even when the ...
15
votes
1answer
9k views

Conflicting results of Type III sum of squares in ANOVA in SAS and R

I'm analyzing data from an unbalanced factorial experiment both with SAS and R. Both SAS and ...
3
votes
2answers
192 views

Averaging images

I want to see if it is possible to analyse openly available images (from google, flickr, etc.), and conclude something from them (the same way one might do this from census data but with images as ...
3
votes
1answer
2k views

Basic question about cross validation

A very basic question about cross validation for Neural Networks. Do I have to create a new network for each fold or do I have to keep the network and incrementally train it with the k-th training ...
1
vote
1answer
380 views

Given a fitted regression model, how to calculate the p-value of a new observation?

(apologies in advance if I abuse any terminology) I have a series of XY data points that I fit with a simple regression and I would like to be able to use this regression to obtain a p-value for the ...
5
votes
2answers
3k views

How to determine the marginal pdf, the posterior?

How to get the marginal pdf of $p(y)$? Do you just integrate out $p({\sigma}^{2})$? Say, the following joint distribution for $y \in {{R}^{d}}$ and ${{\sigma }^{2}}\in {{R}^{d}}$ IG: means inverse ...
6
votes
0answers
2k views

Maximum entropy classifier and sentiment analysis

I am doing a project work in sentiment analysis (on Twitter data) using machine learning approach. In order to find the 'best' way to this I have experimented with naive Bayesian and maximum entropy ...
2
votes
2answers
3k views

Resampling without replacement in R, with a loop

Here is the head of my data set (tjornres): ...
1
vote
2answers
133 views

How is EM used in the sense of data mining on images?

I understand how EM is used in the sense of estimating the Gaussian model that underlies a set of data, but its unclear how this is applicable. I am trying to understand how EM might be used to ...
2
votes
1answer
278 views

Conditional regression for 2 SD below / above the mean

I want to interpret an interaction. Usually a conditional regression analysis is done with 1 SD below/above the mean (see Aiken & West, 1993, p. 18). My result is a contrast with $p=.068$ if I ...
3
votes
2answers
1k views

Dealing with mixed categorical data: e.g. Heritage Health Prize data

Looking at the Heritage Health Prize, the data is structured as follows: Each of the Data Sets will be comprised of tables as follows: ...
2
votes
1answer
2k views

Comparing standard deviations of two dependent samples

As far as I know you can do a F-test ($F = s_1^2/s_2^2$) or a chi-squared test ($\chi^2 = (n-1)(s_1^2/s_2^2$) for testing if the standard deviations of two independent samples are different. But does ...
10
votes
1answer
1k views

Help with SEM modeling (OpenMx, polycor)

I have lots of problem with one data set to which I am trying to apply SEM. We suppose the existence of 5 latent factors A, B, C, D, E, with indicators resp. A1 to A5 (ordered factors), B1 to B3 (...
4
votes
5answers
3k views

Use of robust spread measures such median average deviation and median filters for time series

I have a time series where I need to detect gross anomalies due to coding errors, not small shifts in the structure of the series. I am interested in the most recent data points, not historical data ...
7
votes
4answers
6k views

Choosing between best two attributes with the same information gain when building decision tree

When building a decision tree, suppose that there are two attributes that have the same maximum information gain. Will there be any difference between choosing any of the two attributes to be a ...
2
votes
1answer
320 views

What is the level of measurement of image data?

Question: This is a bit of an abstract question, but bear with me. I am averaging images, to try and deduce what the average image of a specific subject looks like (just out of curiosity, it might ...
9
votes
4answers
9k views

Test for significant difference in ratios of normally distributed random variables

Related to Analysing ratios of variables and How to parameterize the ratio of two normally distributed variables, or the inverse of one?. Suppose I have a number of samples from four different ...
5
votes
1answer
86 views

Average case analysis of learning algorithms

Typically analysis of learning algorithms is in the worst-case setting, for example regret bounds in online learning, or generalisation error bounds in classification. Whilst worst case performance is ...
2
votes
1answer
621 views

Expectation of length of a confidence interval for a proportion

a) For a given significance-level $\alpha$, if we find $\mathop{\mathbb E}(b-a)$ such that $\mathbb P(a \leq X \leq b) \geq 1−\alpha$ for all possible values of $a$ and $b$, from the point of view of ...
5
votes
3answers
2k views

How much sub-questions impact one ordinal question in a survey?

I have a variable Net Promoter Score (NPS) which is an item on a survey, the answer format is ordinal, 0 to 10. Then, there are sub-questions on the same survey, some are ordinal, some are ...
9
votes
2answers
5k views

Remove duplicates from training set for classification

Let us say I have a bunch of rows for a classification problem: $$X_1, ... X_N, Y$$ Where $X_1, ..., X_N$ are the features/predictors and $Y$ is the class the row’s feature combination belongs to. ...
73
votes
4answers
27k views

When to use Fisher and Neyman-Pearson framework?

I've been reading a lot lately about the differences between Fisher's method of hypothesis testing and the Neyman-Pearson school of thought. My question is, ignoring philosophical objections for a ...
3
votes
1answer
320 views

Large performance variance when using back-propagation in neural networks for feature extraction

I'm using a multi-layered neural network for feature extraction (similar to deep belief network). I test the performance of my model with cross-validation. When I'm using back-propagation to train ...
7
votes
1answer
2k views

How are piecewise cubic spline bases constructed?

There are words from the The Elements of Statistical Learning on page 119: It is not hard to show that the following basis represents a cubic spline with knots at $\xi_1$ and $\xi_2$: $h_1(X)=...
0
votes
2answers
3k views

Adjusting data for age and bmi

I am doing a study on the effects of bad blood sugar control on patients. BMI, age, type of diabetes (Type 1 and 2 or gestational diabetes) are all variables. Outcomes include C section, early labour ...
25
votes
1answer
6k views

PCA, LDA, CCA, and PLS

How are PCA, LDA, CCA, and PLS related? They all seem "spectral" and linear algebraic and very well understood (say 50+ years of theory built around them). They are used for very different things (PCA ...
71
votes
2answers
42k views

Solving for regression parameters in closed-form vs gradient descent

In Andrew Ng's machine learning course, he introduces linear regression and logistic regression, and shows how to fit the model parameters using gradient descent and Newton's method. I know gradient ...

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