My Reproducible Pitch

• This slide presentation introduces my shiny app https://pbarry.shinyapps.io/testmatrix/
• Instructions can also be found at https://pbarry.shinyapps.io/firstpres_doc/
• The purpose of the shiny app is to demonstrate interactive inputs and outputs in an R environment
• It uses a user interface and a server incorporated in a single programme app.R
• This example shiny app is based on the concept of matrix multiplication (of two matrices), and also displays a plot of the values of one matrix versus those of the second matrix, depending on the value of a boolean checkbox.

We can define two square n x n matrices in R as follows (we take n=2 here).

Amat<-matrix(c(1,2,3,4),ncol=2)
Bmat<-matrix(c(1,3,5,7),ncol=2)
Amat

     [,1] [,2]
[1,]    1    3
[2,]    2    4

Bmat

     [,1] [,2]
[1,]    1    5
[2,]    3    7

The product of Amat and Bmat in R is given by Amat %*% Bmat

Amat<-matrix(c(1,2,3,4),ncol=2)
Bmat<-matrix(c(1,3,5,7),ncol=2)
Amat%*%Bmat

     [,1] [,2]
[1,]   10   26
[2,]   14   38

The app does the following.

1. The user defines the size of the two matrices to be used (1x1 to 6x6) using an input box
2. Two random matrices of that size are generated
3. The product of these two matrices is calculated, when an action button is pressed
4. Depending on a boolean input checkbox, the product of the matrices is displayed, or a plot of the values defining the second matrix versus the values of the first matrix is shown (where these values are normalized to be between 0 and 1)