Dealing with Duplicates in a Combined Dataframe - duplicates

Question

first of all a big shout-out and big thank you to all in helping to answer my questions. You guys are amazing.
I would need your help once again in Coding with R.
The situation arises with two Dataframes, where Dataframe1 one describes a Portuguese class and Dataframe2 describes a Math class. I do want to find the duplicate (as there are some, as one student takes both classes) and not delete him, but expand the column "Class" by indicating, he is on both classes, something like "Math+Portuguese".
I tried to simplify my Dataframes (in reality they are much bigger, but the final approach should be the sam) by creating two new ones. There is one duplicate (the student where both parents are doctors). I just want to have him one time in the Dataframe, with the wording "Math+Portuguese" in the column "Class".
For the identification of the duplicates, the column "Grades" has to be ignored.
Thank you very much for you help.
All the best,
Alexander
# Creation of Dataset 1 (Portuguese students)
school <- c(rep("S1",7),rep("S2",3))
Age <- c(18,18,19,19,20,20,21,21,22,22)
professionf <- c(rep("teacher",9),rep("doctor",1))
professionm <- c(rep("police",9),rep("doctor",1))
Class <- rep("Portuguese",10)
Grade <- round(runif(10,1,5),0)
DataframeP <- cbind(school, Age, professionf,professionm,Grade,Class)
View(DataframeP)
#Creation of Dataset 2 (Math students)
school <- c(rep("S1",7),rep("S2",3))
Age <- c(18,18,19,19,20,20,21,21,22,22)
professionf <- c(rep("lawyer",9),rep("doctor",1))
professionm <- c(rep("police",9),rep("doctor",1))
Class <- rep("Math",10)
Grade <- round(runif(10,1,5),0)
DataframeM <- cbind(school, Age, professionf,professionm,Grade,Class)
View(DataframeM)
#Combination of the two Dataframes, where the identification of the dupicates should take place
DF_All <- rbind(DataframeM,DataframeP)
View(DF_All)

Answer 1

That should do it, dear Alexander!
library(data.table)
require(dplyr)
df_merged <- merge(x = DataframeP, y = DataframeM, by = c("school", "Age", "professionf", "penter code hererofessionm"), all = TRUE)
df_merged <- within(df_merged, Class.x[Class.x == 'Portuguese' & Class.y == 'Math'] <- 'Portoguese + Math')
df_merged$Class.x = coalesce(df_merged$Class.x, df_merged$Class.y)
df_merged$Grade.x = coalesce(df_merged$Grade.x, df_merged$Grade.y)
df_merged <- df_merged[1:(length(df_merged)-2)]
setnames(df_merged, old = c('Grade.x','Class.x'), new = c('Grade','Class'))
df_merged