In R, how to extract matrix dimension names (or labels) and list those names in another vector?-CodePudding

The answer to this question will help me answer a question I posted earlier today.

In order to run some calculations from an input matrix, I need to be able to extract dimension names and list those names in a separate vector.

Below MWE code runs an example, using package R shiny. Doesn't matter if you input into the matrix or not as 2 default values are randomly generated in any case. I have a section of code (at oe1 <- near the bottom) that extracts the matrix values: after running the App, type "samples.R" in the R Studio console and see output of matrix values. I need to be able to extract the matrix column names and place them in a separate vector (for calculations that will be used in the fuller App this MWE derives from). As shown and explained in the image at the bottom, a snapshot of examining the matrix values in the R Studio console. How can this be done?

MWE code:

library(shiny) 
library(shinyMatrix) 

m <- matrix(runif(2), 1, 2, dimnames = list(c("Values"), c(1:2))) 

ui <- fluidPage(   
  titlePanel("Matrix inputs"),   
  sidebarPanel(     
    width = 6,     
    matrixInput(       
      "sample",       
      value = m,       
      rows = list(extend = FALSE),       
      cols = list(extend = TRUE, names = TRUE, editableNames = TRUE, delete = TRUE),
      class = "numeric"
      )   
    ),   
  mainPanel(     
    width = 6,     
    plotOutput("scatter")   
    ) 
  ) 

server <- function(input, output, session) {   
  
   output$scatter <- renderPlot({plot(1:ncol(input$sample),input$sample,xlab="Nbr",ylab="Values")}) 
  
   oe1 <- reactive({req(input$sample) # <<< capture matrix inputs for function development
          input$sample})
          observeEvent(oe1(),{sample.R <<- oe1()})
   
} 

shinyApp(ui, server)

CodePudding user response：

You may use colnames to get the column names of the matrix.

observeEvent(oe1(),{
    sample.R <<- oe1()
    cm1 <<- colnames(oe1())
})

You can check this vector in the console after running the app.

cm1
[1] "1" "2"

If you are using these values in the app you don't need to use <<-.

CodePudding user response：

We can also do

observeEevent(oe1(), {
       tmp <- oe1()
        sample.R <- tmp
        cm1 <- colnames(tmp)
     })