From 4f84c6fc9c58cfcfeb788e74fbde63549ff20100 Mon Sep 17 00:00:00 2001 From: Gustav Delius Date: Tue, 8 Apr 2014 22:11:14 +0100 Subject: [PATCH 1/2] Fixed some minor typos. --- README.md | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/README.md b/README.md index 6d028906790..ca5dab7efc8 100644 --- a/README.md +++ b/README.md @@ -1,14 +1,14 @@ ### Introduction This second programming assignment will require you to write an R -function is able to cache potentially time-consuming computations. For +function that is able to cache potentially time-consuming computations. For example, taking the mean of a numeric vector is typically a fast operation. However, for a very long vector, it may take too long to compute the mean, especially if it has to be computed repeatedly (e.g. in a loop). If the contents of a vector are not changing, it may make sense to cache the value of the mean so that when we need it again, it can be looked up in the cache rather than recomputed. In this -Programming Assignment will take advantage of the scoping rules of the R +Programming Assignment you will take advantage of the scoping rules of the R language and how they can be manipulated to preserve state inside of an R object. @@ -17,7 +17,7 @@ R object. In this example we introduce the `<<-` operator which can be used to assign a value to an object in an environment that is different from the current environment. Below are two functions that are used to create a -special object that stores a numeric vector and cache's its mean. +special object that stores a numeric vector and caches its mean. The first function, `makeVector` creates a special "vector", which is really a list containing a function to @@ -64,8 +64,8 @@ function. ### Assignment: Caching the Inverse of a Matrix -Matrix inversion is usually a costly computation and their may be some -benefit to caching the inverse of a matrix rather than compute it +Matrix inversion is usually a costly computation and there may be some +benefit to caching the inverse of a matrix rather than computing it repeatedly (there are also alternatives to matrix inversion that we will not discuss here). Your assignment is to write a pair of functions that cache the inverse of a matrix. From 7f657dd22ac20d22698c53b23f0057e1a12c09b7 Mon Sep 17 00:00:00 2001 From: "Roger D. Peng [amelia]" Date: Tue, 22 Apr 2014 10:09:22 -0400 Subject: [PATCH 2/2] More typos --- README.md | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/README.md b/README.md index 81bba09417d..7a8c502a4be 100644 --- a/README.md +++ b/README.md @@ -1,16 +1,16 @@ ### Introduction This second programming assignment will require you to write an R -function that is able to cache potentially time-consuming computations. For -example, taking the mean of a numeric vector is typically a fast +function that is able to cache potentially time-consuming computations. +For example, taking the mean of a numeric vector is typically a fast operation. However, for a very long vector, it may take too long to compute the mean, especially if it has to be computed repeatedly (e.g. in a loop). If the contents of a vector are not changing, it may make sense to cache the value of the mean so that when we need it again, it can be looked up in the cache rather than recomputed. In this -Programming Assignment you will take advantage of the scoping rules of the R -language and how they can be manipulated to preserve state inside of an -R object. +Programming Assignment you will take advantage of the scoping rules of +the R language and how they can be manipulated to preserve state inside +of an R object. ### Example: Caching the Mean of a Vector @@ -76,8 +76,8 @@ Write the following functions: that can cache its inverse. 2. `cacheSolve`: This function computes the inverse of the special "matrix" returned by `makeCacheMatrix` above. If the inverse has - already been calculated (and the matrix has not changed), then the - `cachesolve` should retrieve the inverse from the cache. + already been calculated (and the matrix has not changed), then + `cacheSolve` should retrieve the inverse from the cache. Computing the inverse of a square matrix can be done with the `solve` function in R. For example, if `X` is a square invertible matrix, then