Book Image

Learning Shiny

By : Hernan Resnizky
Book Image

Learning Shiny

By: Hernan Resnizky

Overview of this book

Table of Contents (19 chapters)
Learning Shiny
Credits
About the Author
Acknowledgements
About the Reviewers
www.PacktPub.com
Preface
Free Chapter
1
Introducing R, RStudio, and Shiny
Index

reshape2


reshape2 is a package that consists mainly of two functions: melt and dcast/acast. Generally, it could be said that melt() transforms one row to multiple and shorter rows while dcast() and acast() do exactly the opposite.

The melt() function, basically, transforms one row of data to many by pivoting a set of variables (the measure variables) over a set of other variables (the id variables). The function is called as follows:

melt(dataset,id.vars,measure.vars,variable_name)

The id variables are usually factors or characters while the measure variables are the numeric ones. In fact, this is the behavior by default if none of the arguments are specified. variable_name is the name that adopts the column where the variables are specified (variable by default):

> library(reshape2)
> data(iris)
> melt(iris)
Using Species as id variables
Species      variable    value
1 setosa   Sepal.Length   5.1
2 setosa   Sepal.Length   4.9
3 setosa   Sepal.Length   4.7
4 setosa   Sepal.Length...