how to apply selectively borders to an existing xlsx using openxlsx - openxlsx

Question

The objective is to apply borders to parts of a table using openxlsx. Next I will show the desired output, builded in a way that is not the desired one: printing parts of the table and formating it in each step:
library(openxlsx)
library(tidyverse)
set.seed(15)
###create workbook
wb <- createWorkbook()
addWorksheet(wb, "test2")
#Sample a portion of iris to make it short
iris%>%dplyr::sample_n(15)->sample_iris
#split according to Species
sample_iris%>%filter(Species %in% "setosa")->p1
sample_iris%>%filter(Species %in% "versicolor")->p2
sample_iris%>%filter(Species %in% "virginica")->p3
##write each part and apply borders
writeData(wb, 1,p1, startRow = 1, startCol = 1,borders = "surrounding",borderStyle="thick")
writeData(wb, 1,p2, startRow = 1+dim(p1)[1], startCol = 1,borders = "surrounding",colNames =F,borderStyle="thick")
writeData(wb, 1,p3, startRow = 1+dim(p1)[1]+dim(p2)[1], startCol = 1,borders = "surrounding",colNames =F,borderStyle="thick")
saveWorkbook(wb, "test2.xlsx", overwrite = TRUE)
So "test2.xlsx" is the desired output. The thing is how to achieve it not by generating the file, but to modify an existing file. I mean, if the file "test1.xlsx" is created by
write.xlsx(sample_iris, file = "test1.xlsx")
then, how to apply borders as desired on the already existing file?
Thanks for any guide on this

Answer 1

Next is the code to do the task:
rm(list=ls())
library(tidyverse)
library(openxlsx)
my_borders<-function(wb,sheet_name,a2,vartobrd,borderStyle="thick"){
btop<-createStyle(border=c("top"),borderStyle=borderStyle)
bleft<-createStyle(border=c("left"),borderStyle=borderStyle)
bright<-createStyle(border=c("right"),borderStyle=borderStyle)
bbottom<-createStyle(border=c("bottom"),borderStyle=borderStyle)
blb<-createStyle(border=c("left","bottom"),borderStyle=borderStyle)
bbr<-createStyle(border=c("bottom","right"),borderStyle=borderStyle)
length_box<-dim(a2)[2]
floor_bx<-1:length_box%>%.[-c(1,length_box)]
a2$rnum<-1:dim(a2)[1]
a2%>%group_by_(vartobrd)%>%summarise(min=min(rnum),max=max(rnum))->box_lm
box_lm<-as.data.frame(box_lm)
for(i in seq_along(box_lm[,vartobrd])){
box_lm%>%filter_(paste0(vartobrd, "%in%","'", box_lm[i,vartobrd], "'"))%>%
select(min,max)->minmax_lm
side_indx<-minmax_lm$min:minmax_lm$max
cornerindx<-length(side_indx)
side_indx_sin_corn<-1:(cornerindx-1)
side_cels<-side_indx[side_indx_sin_corn]
nside_cels<-length(side_cels)
corner<-side_indx[cornerindx]
addStyle(wb, sheet=sheet_name, style = bleft, rows=side_cels+1, cols=rep(1,nside_cels))
addStyle(wb, sheet=sheet_name, style = bbottom, rows=rep(minmax_lm$max,length_box-2)+1, cols=floor_bx)
addStyle(wb, sheet=sheet_name, style = bright, rows=side_cels+1, cols=rep(length_box,nside_cels))
addStyle(wb, sheet=sheet_name, style = blb, rows=corner+1, cols=1)
addStyle(wb, sheet=sheet_name, style = bbr, rows=corner+1, cols=length_box)
}
}
#####test the solution
wb <- openxlsx::createWorkbook()
openxlsx::addWorksheet(wb, sheetName = 1)
openxlsx::freezePane(wb, sheet = 1, firstActiveRow = 2)
openxlsx::writeData(wb, x=iris, sheet = 1, colNames =T)
my_borders(wb,sheet_name=1,a2=iris,borderStyle="thick",vartobrd="Species")
openXL(wb)
I appreciate any comments on this.