# Questions tagged [vector-fields]

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### Expected value notation

I come across the notions $\mathrm{E}[wage]$ and $\mathrm{E}[wage_i]$. I would like to clarify if they have different meanings. Take the first expression. $\mathrm{E}[wage]$ could represent the ...
76 views

### Correlation 2D vector fields

Having multiple (hundreds) of 2D flow maps, ie vector fields how would one find statistical correlation between these? Plotting yields, for visualization purposes only: I am thinking about comparing ...
167 views

### How do I get the density of a region in a vector space?

I have a simple problem, which I think must have an easy solution. I have a vector space say with a 1000 dimensions for each vector. Now, I have a large number of sample vectors from this vector ...
51 views

### Extrapolating a 2D vector field in four dimensions

I'm not really sure how to explain this, but I've got several 2D vectors located at points in 4-space and I want to generate a continuous approximation(?) of this. My data looks like this: ...
122 views

### Variance of sum of random vectors - a proof

For nonrandom matrices $A(rXk)$,$B(rXm)$, and $c(rX1)$, how does one show that \newcommand{\Var}{{\rm Var}}\newcommand{\Cov}{{\rm Cov}}\newcommand{\*}{{\times}} \Var(AX+BY+c)=A\Var(X)A′+ B \Var(...
24 views

### Spatio Temporal Interpolation of Vector Fields

I'm looking around for interpolation methods for vector fields, and RBFs seem to be a recommended approach. I've seen ALGLIB specifically mention that it is not suitable for spatio-temporal ...
86 views

### Vector with elements from a uniform distribution, to be made unit

I have a two dimensional constant vector $\mathbf{A} = \left < 2,1 \right>$. Also, I have a vector $\mathbf{e} = \left < \epsilon_x, \epsilon_y\right >$. Both $\epsilon_x$ and $\epsilon_y$ ...
90 views

### Intuition behind word vector representations

How is it possible for a vector space to represent words so that it is coincident to our intuition of words? What does the orthogonality concept in such a space mean precisely? I think we can present ...
91 views

### Constructing feature vectors for clustering from row values

Thank you for some ideas regarding my question below. Background: I have an excel file with each row representing transactions (or transaction id's) in the format below and I am creating a feature ...
162 views

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### Constructing N-dimensional vectors out of point distances

I was wondering if anyone had any insight or information on how one might go about determining point coordinates in an n-dimensional space from point pair distances. For example, say I start with a ...
2k views

### How to test if two sets of vectors are statistically different from each other

I have a set of 2-dimensional vector observations (like to wind vectors), and I have separated them into subsamples based on whether an event that is independent of the observations occurred or not. ...
54 views

### Changing the basis of random variables

Let $X_1$ and $X_2$ be two independent (1-dimensional) random variables and let $Y_1 = f^1(X_1, X_2)$ ($f^1$ is a deterministic function) be a (1-dimensional) random variable too. Question Does ...
579 views

### How to define the covariance for a finite set of vectors in an inner product space space V? What object is it? [closed]

Motivation: This question is motivated by a type of problems in medical imaging and computer vision as follows: suppose we've a set $A$ of points ("shapes") $\{x_1, ...x_d\}$in a Riemannian ...
80 views

### Merge column vectors from the loop in to a single matrix *.mat in matlab [Solved] [closed]

I have an iteration of my algorithm and it gives me a column vector as a result (1899x1 double). I want to form a new matrix composed of these column vectors together sequentially (for example, the ...
111 views

### Detecting a difference in the direction of two groups of vectors

I have two groups of patients, one group obese, one non-obese. I have vectors representing the longitudinal axis of the kidneys in each patient. I am comparing the orientation of the right kidneys ...
32 views

### How would I go about using regression to estimate a change in direction or movement in n-space?

I have a dependent variable which is a position in n-space (so a vector of length n). I want to use regression (or some other method if you have a suggestion) to determine whether independent ...
53 views

### A small help in understanding basic SVM

I am on the course of learning SVM. So, I am having a doubt. Suppose in the case of 2D, a point needs to be classified. So, let say I am having a point x(2,3). So according to the equation wx+b >= 1 ...
1k views

### Difference between Bag of words and Vector space model

I am searching for the intuitive difference between Bag-of-words and vector space model? Is there any relationship exists between bag-of-words and vector space model. I tried searching but couldn't ...
82 views

### What is the term for E[x*y']

I know this is probably a very simple question, but I recall learning that for 2 random vectors, x & y, with mean mx & my, E[(x-mx)(y-my)'] is the covariance & E[xy'] is the correlation ...