1 / 15

Alternative text for elementary statistics

Alternative text for elementary statistics. www.statsoft.com/textbook/stathome.html www.statsoft.com/textbook/stathome.html Elementary Concepts Basic Statistics. Introduction to R. Autumn 2007 Petter Mostad mostad@chalmers.se. What is R? .

fawn
Download Presentation

Alternative text for elementary statistics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Alternative text for elementary statistics • www.statsoft.com/textbook/stathome.html • www.statsoft.com/textbook/stathome.html • Elementary Concepts • Basic Statistics

  2. Introduction to R Autumn 2007 Petter Mostad mostad@chalmers.se

  3. What is R? • A programming language for statistical data analysis called S developed at Bell Labs. Later extended to S+. • R is a free, open source version of S/S+. • Available from www.r-project.org • Under active cooperative development; versions change frequently. • Very popular tool in statistics community: New methods often now implemented there.

  4. Basics of R • Command-driven language • Data (and functions) stored as named objects • Objects can be fairly simple (vectors, matrices) or more comples (assembled from other objects)

  5. Vectors and matrices • Calculations often done on vectors or matrices • Elementwise operations • Subsetting, indexing • Logical indexing

  6. Help and documentation • Use ”An introduction to R” • Some recommended sections: 1.1, 1.7-1.11, 2, 5.1-5.4, 5.8, 6, 7.1, 10.1, 12.1, 12.3 • help(mean) • help.search(”<subject>”) • help.start()

  7. Organizing your computations • R has a ”current directory” • Your objects are contained in your ”current workspace”, which can be saved any time • Keep separate projects in separate workspaces/directories • Keep it tidy!

  8. Graphical visualization • A ”generic” function: plot() • High level commands, like pairs, image, contour... • Lower level commands, adding stuff: points(), lines(), text(), title(), legend()... • plotting characters pch, colors col...

  9. Functions • Most of R consists of functions • The arguments can either be input in the right order, or using argument names • Use help(...) !

  10. Functions related to basic statistics • For every distribution, we may: • Compute the probability density function • Compute the cumulative density function • Simulate random values from the distribution • Compute the quantiles • See for example help(rnorm) • pnorm, pf, pt, pchisq, ….

  11. Doing tests in R • For example t.test(…) can be done in R • Many other tests are readily implemented: prop.test(…), binom.test(…), chisq.test(…), cor.test(…) • help(test) will not work; try help.search(”test”)

  12. Doing ANOVA in R • Considered in R to be a part of linear modelling • Use, for example, anova(lm(Y ~ factor(X1))) anova(lm(Y ~ factor(X1) + factor(X2))) etc.

  13. Writing your own functions • Collecting commands into a function • Arguments to function • Returning result as a list • Assignments within functions • programming: conditional statements, loops (avoid them!) etc... • fix(<myfunction>)

  14. Import and export of data • Useful functions: read.table, write.table • Works with mixed-type data (numbers and text columns) • Works well with tab-separated data (connection to Excel) • scan()

  15. R packages • A package: collection of functions (and data) concerning special application • Contributed from different sources/persons • Can be downloaded from CRAN or BioConductor • must be ”loaded” with library() • search() • help(package = graphics) • Also: Documentation from help.start()

More Related