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Zhuo Yao, Ph.D.

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Category: R

R

R Programming/Text Processing

calsalmon November 3, 2013

http://en.wikibooks.org/wiki/R_Programming/Text_Processing   This page includes all the material you need to deal with strings in R. The section on regular expressions may be useful to…

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R

R-substr, substring

calsalmon November 3, 2013

Retrieve or replace a substring of a character string via the substr and substringfunctions. Additionally, these functions can be used to overwrite a part of a character string.…

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R

Writing a for-loop in R

calsalmon July 15, 2013

by Patrick on 23 March, 2013 in Patrick’s Ponderables There may be no R topic that is more controversial than the humble for-loop. And, to top it off, good help…

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R

Plotting a 3D surface plot with contour map overlay, using R

calsalmon July 2, 2013

I have a 3-tuple data set (X,Y,Z points) that I want to plot using R. I want to create a surface plot from the data,…

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R

Reading in data from an external file

calsalmon July 1, 2013

Reading in data from an external file The data sets: test.txt, cars.txt, test_missing.txt, test_missing_comma.txt, test_fixed.txt, scan.txt, 1. Reading in data from the console using the scan function For very small data vectors it…

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R

Summary statistics by two or more factor variables

calsalmon June 9, 2013

How about this, still using tapply()? It’s more versatile than you knew! with(mtcars, tapply(mpg, list(cyl, gear), sum)) # three four five # four 21.5 215.4 56.4…

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R

Factors in R

calsalmon June 9, 2013

Factors in R Conceptually, factors are variables in R which take on a limited number of different values; such variables are often refered to as…

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R

Frequencies and Crosstabs

calsalmon June 9, 2013

This section describes the creation of frequency and contingency tables from categorical variables, along with tests of independence, measures of association, and methods for graphically…

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R

R- Table Function

calsalmon June 9, 2013

R Tutorial Cyclismo.org Two Way Tables Here we look at some examples of how to work with two way tables. We assume that you can enter…

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R

Open Access .mdb Files with RODBC

calsalmon May 14, 2013

Getting data into R can be done by reading colon separated files (.csv) via the read.table() function. It is also possible to access databases directly…

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