Merging xts objects with repeating column names

Hi!

I am back-testing a trading strategy on the members of a stock index. I have historical stock price date for every years. I would like to merge these time-series objects. My problem is that the index constituents are not the same , therefore I could not simple rbind them. Merging is not an option as well, because it creates separate columns for the same stocks from different years. Could someone suggest me a solution?

Here is an example of my problem:
xts1:

                                  AAPL    AMZ   AA    AXP     
              11/01/2020          100     85     90    70     
              12/01/2020          105     70     80    90     

xts2:

                                  AAPL    AM    AXP     BA
              01/01/2021          108     75     80     50
              02/01/2021          110     60     70     60 

final xts:

                                  AAPL    AMZ   AA    AXP     BA
              11/01/2020          100     85     90    70     NA
              12/01/2020          105     70     80    90     NA
              01/01/2021          108     75     NA    80     50
              02/01/2021          110     60     NA    70     60

Hi @tamas1,
This will get you your desired output with this very simple example but it will be more tedious if there are many mismatched column names (company ticker symbols):

xts1 <- read.table(header=TRUE, text=c("
DATE                AAPL    AMZ   AA    AXP     
'11/01/2020'          100     85     90    70     
'12/01/2020'          105     70     80    90
"))

xts2 <- read.table(header=TRUE, text=c("
DATE              AAPL    AM    AXP     BA
'01/01/2021'          108     75     80     50
'02/01/2021'          110     60     70     60
"))

# Wanted:
#                    AAPL    AMZ   AA    AXP     BA
# 11/01/2020          100     85     90    70     NA
# 12/01/2020          105     70     80    90     NA
# 01/01/2021          108     75     NA    80     50
# 02/01/2021          110     60     NA    70     60

# Identify mismatching column names. Will be tricky if there are many.
setdiff(names(xts1), names(xts2))
#> [1] "AMZ" "AA"

suppressPackageStartupMessages(library(tidyverse))

xts_full <- bind_rows(xts1, xts2)  # cols are matched by name, missing cols filled with NA.
xts_full
#>         DATE AAPL AMZ AA AXP AM BA
#> 1 11/01/2020  100  85 90  70 NA NA
#> 2 12/01/2020  105  70 80  90 NA NA
#> 3 01/01/2021  108  NA NA  80 75 50
#> 4 02/01/2021  110  NA NA  70 60 60

# Column pairs to be merged (same company with different ticker code)
# AMZ = AM

xts_full %>% 
  rowwise() %>% 
  mutate(AMZ = sum(c(AMZ, AM), na.rm=TRUE)) %>% 
  select(-AM)
#> # A tibble: 4 x 6
#> # Rowwise: 
#>   DATE        AAPL   AMZ    AA   AXP    BA
#>   <chr>      <int> <int> <int> <int> <int>
#> 1 11/01/2020   100    85    90    70    NA
#> 2 12/01/2020   105    70    80    90    NA
#> 3 01/01/2021   108    75    NA    80    50
#> 4 02/01/2021   110    60    NA    70    60

Created on 2021-10-03 by the reprex package (v2.0.1)