Is there a specific function in R to merge 2 vectors

Question

I have two vectors, one that contains a list of variables, and one that contains dates, such as

Variables_Pays <- c("PIB", "ConsommationPrivee","ConsommationPubliques",
                    "FBCF","ProductionIndustrielle","Inflation","InflationSousJacente",
                    "PrixProductionIndustrielle","CoutHoraireTravail")
Annee_Pays <- c("2000","2001")

I want to merge them to have a vector with each variable indexed by my date, that is my desired output is

> Colonnes_Pays_Principaux
 [1] "PIB_2020"                        "PIB_2021"                        "ConsommationPrivee_2020"        
 [4] "ConsommationPrivee_2021"         "ConsommationPubliques_2020"      "ConsommationPubliques_2021"     
 [7] "FBCF_2020"                       "FBCF_2021"                       "ProductionIndustrielle_2020"    
[10] "ProductionIndustrielle_2021"     "Inflation_2020"                  "Inflation_2021"                 
[13] "InflationSousJacente_2020"       "InflationSousJacente_2021"       "PrixProductionIndustrielle_2020"
[16] "PrixProductionIndustrielle_2021" "CoutHoraireTravail_2020"         "CoutHoraireTravail_2021" 

Is there a simpler / more readabl way than a double for loop as I have tried and succeeded below ?

Colonnes_Pays_Principaux <- vector()
for (Variable in (1:length(Variables_Pays))){
  for (Annee in (1:length(Annee_Pays))){
     Colonnes_Pays_Principaux=
       append(Colonnes_Pays_Principaux,
              paste(Variables_Pays[Variable],Annee_Pays[Annee],sep="_")
              )
  }
}

Answer 1

No real need to go beyond the basics here! Use paste for pasting the strings and rep to repeat either Annee_Pays och Variables_Pays to get all combinations:

Variables_Pays <- c("PIB", "ConsommationPrivee","ConsommationPubliques",
                   "FBCF","ProductionIndustrielle","Inflation","InflationSousJacente",
                    "PrixProductionIndustrielle","CoutHoraireTravail")
Annee_Pays <- c("2000","2001")

# To get this is the same order as in your example:
paste(rep(Variables_Pays, rep(2, length(Variables_Pays))), Annee_Pays, sep = "_")

# Alternative order:
paste(Variables_Pays, rep(Annee_Pays, rep(length(Variables_Pays), 2)), sep = "_")

# Or, if order doesn't matter too much:
paste(Variables_Pays, rep(Annee_Pays, length(Variables_Pays)), sep = "_")

Answer 2

expand.grid will create a data frame with all combinations of the two vectors.

with(
  expand.grid(Variables_Pays, Annee_Pays),
  paste0(Var1, "_", Var2)
)
#>  [1] "PIB_2000"                        "ConsommationPrivee_2000"        
#>  [3] "ConsommationPubliques_2000"      "FBCF_2000"                      
#>  [5] "ProductionIndustrielle_2000"     "Inflation_2000"                 
#>  [7] "InflationSousJacente_2000"       "PrixProductionIndustrielle_2000"
#>  [9] "CoutHoraireTravail_2000"         "PIB_2001"                       
#> [11] "ConsommationPrivee_2001"         "ConsommationPubliques_2001"     
#> [13] "FBCF_2001"                       "ProductionIndustrielle_2001"    
#> [15] "Inflation_2001"                  "InflationSousJacente_2001"      
#> [17] "PrixProductionIndustrielle_2001" "CoutHoraireTravail_2001" 

Answer 3

In base R:

Variables_Pays <- c("PIB", "ConsommationPrivee","ConsommationPubliques",
                    "FBCF","ProductionIndustrielle","Inflation","InflationSousJacente",
                    "PrixProductionIndustrielle","CoutHoraireTravail")
Annee_Pays <- c("2000","2001")
cbind(paste(Variables_Pays, Annee_Pays,sep="_"),paste(Variables_Pays, rev(Annee_Pays),sep="_")

Answer 4

We can use outer :

c(t(outer(Variables_Pays, Annee_Pays, paste, sep = '_')))

# [1] "PIB_2000"                        "PIB_2001"                       
# [3] "ConsommationPrivee_2000"         "ConsommationPrivee_2001"        
# [5] "ConsommationPubliques_2000"      "ConsommationPubliques_2001"     
# [7] "FBCF_2000"                       "FBCF_2001"                      
# [9] "ProductionIndustrielle_2000"     "ProductionIndustrielle_2001"    
#[11] "Inflation_2000"                  "Inflation_2001"                 
#[13] "InflationSousJacente_2000"       "InflationSousJacente_2001"      
#[15] "PrixProductionIndustrielle_2000" "PrixProductionIndustrielle_2001"
#[17] "CoutHoraireTravail_2000"         "CoutHoraireTravail_2001"