Shiny - runif function inside reactive loop - r

Question

hope someone can help with this one:
My code below was returning a dinamic table as I intend, but when I created the for loop to assign individually random numbers to each [k,p] position in the table all the calculations stop and I see an empty UI.
If instead of
rv$MCProbTable[[k,p]] = round(as.numeric(stats::runif(1,0,100)), 3)
I use for example
rv$MCProbTable[[k,p]] = 2
I see "2" allocated in each position in the table, what is close to what I want and shows that everything is working up to the runif application. So is it an issue with the function? Or most likely it is the reactive for loop that isn't set properly?
Thanks and hope this is an easy one!
## LIBRARIES
library(tidyverse)
library(stats)
library(data.table)
library(triangle)
library(base)
library(matrixStats)
library(ggplot2)
library(ggthemes)
library(readxl)
library(httr)
library(writexl)
library(shiny)
ExcelTemplate <- tempfile(fileext = ".xlsx")
GET(url = "https://www.openmontecarlo.com/SampleS.xlsx",write_disk(ExcelTemplate))
defaultRR <- read_xlsx(ExcelTemplate)
## DEFINE UI
ui <- fluidPage(
numericInput("ISvModels", label = h3("Select how many scenarios to run in the model:"),value=10,min=5,max=10000),
hr(),
mainPanel(
fluidRow(
p("vModels"),
textOutput("vModelsText"),
p("vtModels"),
textOutput("vtModelsText"),
p("Scenarios"),
textOutput("SnScenarios"),
h3(strong("ProbTable")),
br(),
dataTableOutput("SMCProbTable"),
hr()
)
)
)
server <- function(input, output, session) {
## CREATE DEFAULT RR AND REACTIVE VARIABLES
rv <- reactiveValues(
vModels = 10,
nScenarios = 10,
vtModelScenarios = NULL,
RRDT = data.frame(),
nRisks = 1,
MCProbTable = data.frame(),
p = 1,
k = 1
)
## PROCESS MODELS INPUT
observe({rv$vModels <- as.numeric(unlist(input$ISvModels))})
output$vModelsText <- renderPrint({unlist(rv$vModels)})
qtModels <- reactive({length(unlist(rv$vModels))})
output$qtModelsText <- renderPrint({unlist(qtModels())})
vtModels <- reactive({paste0("M",1:qtModels()," n = ",rv$vModels," scenarios")})
output$vtModelsText <- renderPrint({unlist(vtModels())})
## RR TABLE
observe({rv$nRisks <- nrow(defaultRR)})
###############################################################################################################
## CALCULATE SCENARIOS - CREATE DATA TABLES AND TEXT VECTORS FOR EACH SCENARIO
## Vectors for SINGLE scenario
observe({rv$nScenarios <- rv$vModels})
observe({rv$vtModelScenarios <- paste0("Scenario ",1:rv$nScenarios,"/",rv$vModels)})
## CREATE PROBABILITY TABLE AND CALCULATE PROBABILITIES
observe({rv$MCProbTable <- data.frame(matrix(nrow=rv$nRisks,ncol=rv$nScenarios))})
observe({rownames(rv$MCProbTable) <- rv$RRDT$ID})
observe({colnames(rv$MCProbTable) <- rv$vtModelScenarios})
observe({
for (p in 1:rv$nScenarios){
for (k in 1:rv$nRisks){
rv$MCProbTable[[k,p]] = round(as.numeric(stats::runif(1,0,100)), 3)
}
}
})
output$SMCProbTable <- renderDataTable({rv$MCProbTable})
}
# Run the app ----
shinyApp(ui = ui, server = server)

Answer 1

In your for loop, use isolate()
for (p in 1:rv$nScenarios){
for (k in 1:rv$nRisks){
isolate(
rv$MCProbTable[k,p] <- round(as.numeric(stats::runif(1,0,100)), 3)
)
}
}