StaMPS-Visualizer, SNAP-StaMPS Workflow

thanks for reporting the issue with the gcc and or g++ version, on my system (standard installtion of Ubuntu 20 LTS) i get these outputs:

thho@kuburock:~$ dpkg --list | grep compiler
ii  g++                                                         4:9.3.0-1ubuntu2                            amd64        GNU C++ compiler
ii  g++-9                                                       9.3.0-10ubuntu2                             amd64        GNU C++ compiler
ii  gcc                                                         4:9.3.0-1ubuntu2                            amd64        GNU C compiler
ii  gcc-9                                                       9.3.0-10ubuntu2                             amd64        GNU C compiler
ii  gfortran                                                    4:9.3.0-1ubuntu2                            amd64        GNU Fortran 95 compiler
ii  gfortran-9                                                  9.3.0-10ubuntu2                             amd64        GNU Fortran compiler
ii  libllvm10:amd64                                             1:10.0.0-4ubuntu1                           amd64        Modular compiler and toolchain technologies, runtime library
ii  libllvm10:i386                                              1:10.0.0-4ubuntu1                           i386         Modular compiler and toolchain technologies, runtime library
ii  libllvm9:amd64                                              1:9.0.1-12                                  amd64        Modular compiler and toolchain technologies, runtime library
ii  libparams-validationcompiler-perl                           0.30-1                                      all          module to build an optimized subroutine parameter validator
ii  libxkbcommon0:amd64                                         0.10.0-1                                    amd64        library interface to the XKB compiler - shared library

For me it looks like gcc and g++ is the same on our systems. Anyway, have you tried to make a full new installation of R +RStudio, with the latest version i found it pretty straight forward:

## R and RStudio
sudo apt update
sudo apt -y install r-base gdebi-core

#download the Rstudio *.deb package from the official Rstudio websit
cd Downloads
sudo gdebi rstudio-1.2.5019-amd64.deb

Regarding your question how to subset points after exporting the csv, check this script, where roi.kml are your polygons of the locations you want to extract the points you are interested in.:

###########################
###subset ts plot export###
###########################
library(sp)
library(rgdal)
library(rgeos)

#read subsetpolygon
roi <- readOGR("/home/user/studysite/roi.kml")
#read exported .csv
pnts <- read.csv("/home/user/ISNAR_master_date/stamps_tsexport.csv")
#create spatial object
lon <- pnts$export_res_1[2:nrow(pnts)]
lat <- pnts$export_res_2[2:nrow(pnts)]
loc <- data.frame(lon, lat)
pnts.geo <- SpatialPointsDataFrame(loc, pnts[2:nrow(pnts), ],
            proj4string = CRS("+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs"))
#spatial subset
pnts.sub <- pnts.geo[roi, ]
#create table from spatial subset
sub.csv <- rbind(pnts[1, ], pnts.sub@data)
#export csv to StaMPS-Visualizer application
#adapt path to your machine
write.table(sub.csv, file = "/home/user/stamps_visualizer/stusi/stamps_tsexport.csv",
            row.names = F, col.names = T, sep = ",")