# Questions tagged [numerics]

Also known as Numerical Analysis, Numerics aims to provide methods and algorithms for numerical computations.

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### Establish numerical equivalence of statistical model across software

we are trying to establish numerical equivalence (within reasonable precision) for selected statistical models across programming languages such as SAS, R & Python or even different packages ...
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### How can I compute rectangular confidence regions for parameters using R?

Simultaneous confidence regions for multivariate parameters (say, a confidence region for multivariate mean, or for regression parameters) usually find an elliptical region when the parameters' ...
• 1,063
1 vote
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### Can I make Stata run lasso faster?

I am trying to run a lasso in Stata. I have 1.5 million observations and 1700 variables. Stata is running too slow. I am in 36th grid after 4 days. And get slower ever grid. I am using a 98GB Memory, ...
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### log(1 - softmax(X))? [closed]

Let $\vec X$ be a vector. The $\vec V = \mathrm{logsoftmax}(\vec{X})$ function is defined as: $$v_i = \ln\left(\frac{e^{x_i}}{\sum_i e^{x_i}}\right)$$ This is provided in machine learning numerical ...
• 3,358
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### Time series reference - Estimating ARIMA models using the Yule-Walker equations and Durbin-Levinson algorithm

I am doing some research related to time-series analysis, and hence was trying to find some good examples of implementations of the common estimation algorithms. For example, I wanted to fit some ...
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### Reference request - time series analysis book with numerical algorithms

I am working on some applications of time series, and I wanted to find a book that has the numerical algorithms or pseudocode for computing things like AR models, and ARIMA models, using nonlinear ...
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### Why is my QR decomposition updating code numerically off?

I apologize if this is the wrong place for this question; there are a number of potential points of failure each of which suggest either Math StackExchange or StackOverflow or here, but since the ...
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• 3,358
1 vote
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### How does the choice of norm affect the condition of a problem?

we know that for a differentiable problem, the absolute condition number is the norm of its jacobian i.e. ||J||. We also know that a well-conditioned problem typically has a small condition number. ...
799 views

### Inverse-normal CDF approximation in Excel, Python or R

I read that the implementations of Inverse-normal cumulative distribution function (CDF) /quantile / ppf in R, Python (scipy) and Excel give similar results. However, I can't find the very formulae ...
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119 views

### Why does lasso return unstable features when using the same data?

I am using scikit-learn to shrink my data set having around 800 features. It is a very noisy data (market and economic data) To my best knowledge, lasso returns same features for the same data set. ...
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176 views

### Intuition about a coupon problem were we ask for the distribution of the unique coupons when the number of draws is fixed

Alternative viewpoint of the coupon collectors problem In the coupon collectors problem we draw from a collection of $n$ coupons, with replacement and ask the question how many draws $K$ it takes to ...
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345 views

### Why is it much quicker to compute ridge regression than regular linear regression? [duplicate]

By my understanding, for a matrix with n samples and p features: Ridge regression using cholesky takes O(p^3) time Ordinary linear regression takes O(p^3) time Singular value decomposition if u, v ...
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547 views

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### adding a small constant to the diagonals of a matrix to stabilize

I have a large correlation matrix (110x110) with some small eigenvalues (about 20 < 0.1). It has been suggested that adding a constant (about 0.1) to the diagonals will help to stabilize the matrix....
278 views

### downsampling a kde / combining kde and histogram

I'm calculating a KDE of one parameter (y, particle density) in bins of another parameter (x, distance from the origin). At ...
1 vote
32 views

### Model or numerical inaccuracy in R package distr

With the goal to have an "outlier"-aware normal distribution, I build a simple univariate mixing model of normal and uniform distributions: ...
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1 vote
296 views

### NUTS Drawing samples from slice sampler; how to keep bounds on log scale?

I'm currently working to adapt the No U-Turn Sampler from this paper for a model I'm working on. The No-U Turn sampler augments the typical hamiltonian system by incorporating a slice variable $u$ ...
1 vote
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