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Tavis Rudd  committed efb6bef

initial import

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File exercises/README.org

+* hello world
+Start the R interpreter and print the string "hello world"
+* hello.world function
+Create a function called hello.world that does what you did manually
+in the previous exercise. 
+* create an anonymous version of the same function
+* use Google to figure out what R's rules are for naming variables and functions
+* hello(name) function
+Create a variant of the previous function that accepts a `name`
+parameter and prints "Hello Mary", "Hello Lamb", etc. 
+
+Hint: you'll need to figure out how to concatenate/join strings
+* hello(name) with a default argument
+Give the `name` argument a default value.
+* create a `vector` of the following strings and assign it to a variable
+"Mary", "had", "a", "little", "lamb"
+* use help.search to find a function that can convert each element in that vector to uppercase 
+* find a function that will give you the length of the vector
+* figure out the syntax to get the third element in the vector
+* create a function that applies another function to each element in a vector
+* find a function that will create a sequence of integers
+This is like the `range` function in Python.
+* use that function and the `matrix` function to create a 4 x 5 matrix of the first 20 natural numbers
+* figure out the syntax to get the matrix element at row 2, col 3
+* multiply every element in the matrix by 3 
+* find a function that gives you the dimensions of the matrix
+* convert this matrix to a vector
+* create a Boolean matrix of the same size 
+... that indicates whether the elements in our first matrix are > 13
+* use the Boolean matrix to take a subset of our first matrix
+... where the condition is true
+... and where it is false
+* what is the type of the subset
+* figure out how to create a random sample of 100 integers
+* take a random sample of five elements from your first matrix
+* find the built-in dataset `swiss` and the help information about it
+* what are the `type`, `dimensions`, `structure`, and `dimension names` of this dataset
+* figure out how to access each column of this dataset individually
+* show the first and last six elements of this dataset
+hint: there are built in functions that will do this for you