R Programming

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R Programming
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• R can be downloaded at the following link
• http//cran.r-project.org/
• You will most likely click on Windows (95 or
• later).
• Click on base.
• Save the file R-2.4.1-win32.exe. This is about
  a 20 megabyte file.

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Background

• R is a system for statistical analysis and
  graphics.
• R was heavily influenced by 2 languages S and
  Scheme
• R is freeware!

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When you run R
The prompt where you can enter commands.
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Creating Variables

• Variable names must start with a letter. They
• may contain numbers, periods. They cannot
• contain ,?,underscore, etc.

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Creating a vector or array
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Manipulating Arrays
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Descriptive Statistics
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help.search

• Suppose I wonder if theres a way to find the
• interquartile range (IQR). I may not be sure
• about the command to get that.

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help

• Now that I know what the function is called, I
• can read more about the documentation.

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Sampling
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Random Number Generation
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Cumulative Probability
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Quantiles (aka Percentiles)
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Density

• Caution! For continuous
• distributions, this is
• not a probability but the
• height of the pdf. For
• discrete distributions, this
• is a probability.

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Chi-Square? Exponential?

• There are many other distributions as well. You
  have
• to search the documentation to find the base
  word.
• But you will probably have r? p? q? d? for
  finding
• various aspects about the distribution. Also be
• careful that you understand what parameters you
• need to give it.

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Histograms
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Boxplots
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Also

• We can also create
• pie charts (use the function pie)
• bar charts (use the function barplot)
• stem and leaf plots (use the function stem)
• To the best of my knowledge, I dont think that
• there is a way to make a dotplot.

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Scatterplots
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Matrices
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Running R from a file

• Obviously if we have a number of operations
• we want to run, it would not be best to type
• them individually from the command prompt.
• We could make a mistake and would then have
• to retype them.

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• To run a program from a file, place all
• commands that you would normally run from
• the command prompt in a text file. Name the
• file with a .r extention.

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From the file menu
Select Source R code
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• Find the .r file that contains your code and
• then select open.
• Your code will be compiled.

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Comments

• In the file that contains your code, you may
• want to place comments.
• To do so, place a in front of what you want
• commented out.

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Creating Functions

• Example

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Notice that inside the vector y was created
inside the function and then outside the
function it reverts back to what it was before.
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Reading data from a file

• datafile.dat

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Lists

• Lists can contain various
• amounts and type of
• information.

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Additional Functions

• Regression lm or lsfit
• t-test t.test one and two sample tests.
• test for proportions binom.test and also
  prop.test - These will do both one and two
  sample tests and find confidence intervals.
• chi-square test for independence chisq.test