Object Oriented Programming in Matlab: Typical Workflow for Defining Class

This tutorial presents an example discussing the typical workflow of object oriented programming in Matlab. Read more ›

Posted in How-to, Matlab Tagged with: ,

Degree of Freedom For Sample Variance: (n-1) instead of n

This article explain why the degree of freedom for sample variance is (n-1) instead of n.

Consider n observations, X_1,X_2,\cdots,X_n, of a random variable X . The formula for calculating sample mean and sample variance are Read more ›

Posted in Knowledge, Mathematics Tagged with:

Mathematics Underlying Principal Component Analysis

This tutorial covers mathematics underlying principal component analysis, including definition of PCs, how to find PCs, and derivation of PCs.

1  Introduction to Principal Component Analysis

1.1  Main idea of Principal Component Analysis

The central idea of principal component analysis (PCA) is to reduce the dimensionality of a data set consisting of a large number of interrelated variables, while retaining as much as possible of the variation present in the data set.

This is achieved by transforming the original set of variables to a new set of variables, the principal components (PCs), which are uncorrelated, and which are ordered so that the first a few retain most of the variation present in all the original variables. Read more ›

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Simple Handling of Data Frame in R

Some simple handling of data frame in R are demonstrated in this tutorial. Read more ›

Posted in How-to, R

An Introduction to Basic Plots in R

This tutorial introduces basic plots in R, including scatter, pie, bar, box, dot, strip, and so on.

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Posted in How-to, R

A Starting Tutorial for R Beginners

As a starting tutorial for R beginners, this article lists some basic and commonly used R commands. Read more ›

Posted in How-to, R

Install R Packages

This tutorial teaches you how to install R packages, based on your system access privilege.

 Suppose we want to install the zoo package. Read more ›

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Accurately Control Excel Chart Position by Matlab

This article tells how to accurately control Excel chart position by Matlab using row and column numbers.

Sometimes we want to align, in Excel spreadsheet, a chart with a cell which, for example, may contain a label for the chart. We can easily drag (with mouse) the chart to make it aligned with the cell, but it may not be so easy to do this by program. The challenge here is that in Excel spreadsheet a cell position is expressed in row and columns, while a chart position is expressed in points. Depending on the screen resolution, the number of points corresponding to one row or column may vary on different computers. When we want to insert a large amount of charts into a sheet by program, exact positioning of these charts will be a headache. This tutorial teaches you how to programmingly obtain and position the chart in terms of row/column numbers. Read more ›

Posted in How-to, Matlab Tagged with: , ,

Eclipse as IDE for Python Programming

In this tutorial, a step-by-step instruction is presented about how to use Eclipse as IDE for Python programming, through PyDev, the specific plugin for Python language.

Background

Eclipse is an open source Integrated Development Environment (IDE). As with Microsoft's Visual Studio product, Eclipse is programming language-agnostic and supports any language having a suitable plugin for the IDE platform. The Eclipse's plugin for Python language is PyDev.

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Division of Electricity Market in United States

This article briefly describes the geological division of electricity market in United States. Read more ›

Posted in Electricity, Energy Commodity, Knowledge Tagged with:

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