Problem loading packages while deploying an R Shiny app - shiny

Question

I was trying to deploy an R Shiny app that works perfectly when I run it locally. But when I deploy the app, it shows an error message in some of the outputs: "Error: An error has occurred. Check your logs or contact the app author for clarification.".
After reading a few threads, I think it has to do with the loading of the packages.
I am using the following packages:
library(shiny)
library(magrittr)
library(shinyjs)
library(DT)
library(ggthemes)
library(shinythemes)
library(r2symbols)
library(caret)
# install.packages("PresenceAbsence")
library(glmnet)
library(tidyverse)
# install.packages("devtools")
I got the following warnings while deploying the app from a fresh new session. I'm not particularly clear about what is going wrong (since the app works on my R session). Could you please suggest to me things I should try to get the app work on the server too?
Loading required package: shiny
Warning: package ‘shiny’ was built under R version 3.6.3
Warning: package ‘shinyjs’ was built under R version 3.6.3
You can use shinyjs to call your own JavaScript functions:
https://deanattali.com/shinyjs/extend
Attaching package: ‘shinyjs’
The following object is masked from ‘package:shiny’:
runExample
The following objects are masked from ‘package:methods’:
removeClass, show
Warning: package ‘DT’ was built under R version 3.6.3
Attaching package: ‘DT’
The following objects are masked from ‘package:shiny’:
dataTableOutput, renderDataTable
Warning: replacing previous import ‘vctrs::data_frame’ by ‘tibble::data_frame’ when loading ‘dplyr’
Warning: package ‘ggthemes’ was built under R version 3.6.3
Warning: package ‘shinythemes’ was built under R version 3.6.3
Warning: package ‘r2symbols’ was built under R version 3.6.3
Attaching package: ‘r2symbols’
The following object is masked from ‘package:ggplot2’:
sym
Warning: package ‘caret’ was built under R version 3.6.3
Loading required package: lattice
Warning: package ‘lattice’ was built under R version 3.6.3
Attaching package: ‘PresenceAbsence’
The following objects are masked from ‘package:caret’:
sensitivity, specificity
Warning: package ‘glmnet’ was built under R version 3.6.3
Loading required package: Matrix
Loaded glmnet 4.0-2
Warning: package ‘tidyverse’ was built under R version 3.6.3
-- Attaching packages -------------------------------------------------------------------------- tidyverse 1.3.0 --
v tibble 3.0.4 v dplyr 1.0.0
v tidyr 1.0.2 v stringr 1.4.0
v readr 1.3.1 v forcats 0.4.0
v purrr 0.3.3
Warning: package ‘tibble’ was built under R version 3.6.3
Warning: package ‘dplyr’ was built under R version 3.6.3
-- Conflicts ----------------------------------------------------------------------------- tidyverse_conflicts() --
x tidyr::expand() masks Matrix::expand()
x tidyr::extract() masks magrittr::extract()
x dplyr::filter() masks stats::filter()
x dplyr::lag() masks stats::lag()
x purrr::lift() masks caret::lift()
x tidyr::pack() masks Matrix::pack()
x purrr::set_names() masks magrittr::set_names()
x dplyr::sym() masks r2symbols::sym(), ggplot2::sym()
x tidyr::unpack() masks Matrix::unpack()
Listening on http://127.0.0.1:6757
More details:
I also mention my output in the server section that does not show up when deployed to the Shiny server but works when run from the local PC. The pred_prob_func() uses a random forest from caret package and gets a predicted probability using a random forest model (ranger). I'm not even sure that package loading is a problem but I guess so. However, I don't know why it would work on my PC and not on the Shiny server. Problems in versions?
Outputs:
# Heatmap predicted probabilities
output$Heatmap_predicted_probabilities <- renderPlot({
plot(x=seq(0,1,0.01), y=rep(0,101), main="Heatmap of predicted probabilities", xlab="The square cross symbol represents the predicted probability based on input values on the dashboard", ylab="", xlim=c(0,1), ylim=c(-0.1,0.1), yaxt="n", bty="n", pch=15, cex=20, col=hsv(0.05, seq(0,1,length.out = 101), 0.80))
points(x=pred_prob_func(input_list())$pred_prob, y=0, lwd=2, pch=7, cex=4)
})

Answer 1

I found the solution and I thought I'd post it here for others who may face the same problem in the future. Apparently, it wasn't a problem of versions. When I ran the app with only calling the 'caret' package it worked fine on my local PC. But it didn't work when uploaded to the Shiny server. I realized it's not enough to call only the 'caret' package but I also need to call the 'ranger' library because I was doing a random forest using 'caret' that used 'ranger'. Although it works without calling 'ranger' separately on my local PC, the app only runs smoothly on the server when I add both these lines:
library(ranger)
library(caret)