# Articles by Al Asaad

### R and Python: Gradient Descent

December 22, 2015 |

One of the problems often dealt in Statistics is minimization of the objective function. And contrary to the linear models, there is no analytical solution for models that are nonlinear on the parameters such as logistic regression, neural networks, and nonlinear regression models (like Michaelis-Menten model). In this situation, we ... [Read more...]

### R and Python: Theory of Linear Least Squares

December 15, 2015 |

In my previous article, we talked about implementations of linear regression models in R, Python and SAS. On the theoretical sides, however, I briefly mentioned the estimation procedure for the parameter $\boldsymbol{\beta}$. So to help us understand how software does the estimation procedure, we'll look at the mathematics behind ... [Read more...]

### R, Python, and SAS: Getting Started with Linear Regression

August 16, 2015 |

Consider the linear regression model, $$y_i=f_i(\boldsymbol{x}|\boldsymbol{\beta})+\varepsilon_i,$$ where $y_i$ is the response or the dependent variable at the $i$th case, $i=1,\cdots, N$ and the predictor or the independent variable is the $\boldsymbol{x}$ term defined in the mean function $... [Read more...] ### Parametric Inference: Karlin-Rubin Theorem July 20, 2015 | A family of pdfs or pmfs$\{g(t|\theta):\theta\in\Theta\}$for a univariate random variable$T$with real-valued parameter$\theta$has a monotone likelihood ratio (MLR) if, for every$\theta_2__\theta_1$,$g(t|\theta_2)/g(t|\theta_1)$is a monotone (nonincreasing or nondecreasing) function of$t$on$\{t:... [Read more...]

### R: Canonical Correlation Analysis on Imaging

January 5, 2015 |

In imaging, we deal with multivariate data, like in array form with several spectral bands. And trying to come up with interpretation across correlations of its dimensions is very challenging, if not impossible. For example let's recall the number of s... [Read more...]

### R: Principal Component Analysis on Imaging

December 25, 2014 |

Ever wonder what's the mathematics behind face recognition on most gadgets like digital camera and smartphones? Well for most part it has something to do with statistics. One statistical tool that is capable of doing such feature is the Principal Component Analysis (PCA). In this post, however, we will not ... [Read more...]

### R: k-Means Clustering on Imaging

September 11, 2014 |

Enough with the theory we recently published, let's take a break and have fun on the application of Statistics used in Data Mining and Machine Learning, the k-Means Clustering.k-means clustering is a method of vector quantization, originally from signa... [Read more...]

### R: Interval Estimation of the Population Mean

June 14, 2013 |

Interval estimation of the population mean can be computed from functions of the following R packages:stats - contains the t.test;TeachingDemos - contains the z.test; and,BSDA - contains the zsum.test and tsum.test.The t.test of the stats package is a ... [Read more...]

### R: Measures of Skewness and Kurtosis

June 10, 2013 |

Skewness and kurtosis in R are available in the moments package (to install a package, click here), and these are:Skewness - skewness; and,Kurtosis - kurtosis.Example 1. Mirra is interested on the elapse time (in minutes) she spends on riding a tricycl... [Read more...]

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