R-code related question

Posit Professional & Hosted Products shinyapps.io
,
1

library(shiny)
library(shinythemes)
library(shinydashboard)

ui <- fluidPage(

navbarPage(title = "DETERMINANTS CALCULATOR",
theme = shinytheme("flatly"),
tabPanel("Home",
navlistPanel(

          tags$h1("Determinants", style = "font-weight: bold; text-align; center;"),
           sidebarPanel(
           selectInput("matrix", "Choose a matrix dimension:"),
                c("2x2", "3x3"),
           submitButton("trigger", "Set as Matrix")
   ),
   )
   )
   ),
         tabPanel("About",
                  sidebarPanel(
                    h2("About the App", style = "font-weight: bold;"),
  )
)

)

I am trying to figure out how to insert a "Selection Option" for my Matrix Calculator as I stumbled upon an error, it says that "Error in choicesWithNames(choices) :
argument "choices" is missing, with no default"

I wish to create a selectioninput, whereas to limit my matrix to 2x2 and 3x3. However, I still cannot figure out how I can move from the next progress as I am stucked with this error since yesterday. I also wish to know for a possible insight to my project as I am learning R/shinyapp. My app is a Determinant Calculator.

2

image

The error is here.

3

image
For reference, this is what I wish to achieve.

4

Your brackets are out of whack.

selectInput("matrix", "Choose a matrix dimension:",
                c("2x2", "3x3"))