Merging variables

On Jun 6, 2016, at 8:29 AM, G.Maubach at weinwolf.de wrote:

Hi All,

I merged two datasets:

ds_merge1 <- merge(x = ds_bw_customer_4_match, y = 
ds_zww_customer_4_match,
 by.x = "customer", by.y = "customer",
 all.x = TRUE, all.y = FALSE)

R created a new dataset with the variables customer.x and customer.y. I 
would like to merge these two variable back together. I wrote a little 
function (code can be run) for it:

-- cut --

customer.x <- c("Miller", "Smith", NA,    "Bird", NA)
customer.y <- c("Miller",  NA,     "Doe", "Fish", NA)
ds_test <- data.frame(customer.x, customer.y, stringsAsFactors = FALSE)

t_merge_variables <-
 function(dataset,
          var1,
          var2,
          merged_var) {

   # Initialize
   dataset[[merged_var]] = rep(NA, nrow(dataset))
   dataset[["mismatch"]] = rep(NA, nrow(dataset))

   for (i in 1:nrow(dataset)) {

     # Check 1: var1 missing, var2 missing
     if (is.na(dataset[[i, var1]]) &
         is.na(dataset[[i, var2]])) {
       dataset[["mismatch"]] <- 1  # var1 & var2 are missing

     # Check 2: var1 filled, var2 missing
     } else if (!is.na(dataset[[i, var1]]) &
                is.na(dataset[[i, var2]])) {
       dataset[[i, merged_var]] <- dataset[[i, var1]]
       dataset[["mismatch"]] <- 0

     # Check 3: var1 missing, var2 filled
     } else if (is.na(dataset[[i, var1]]) &
                !is.na(dataset[i, var2])) {
       dataset[[i, merged_var]] <- dataset[[i, var2]]
       dataset[["mismatch"]] <-  0

     # Check 4: var1 == var2
     } else if (dataset[[i, var1]] == dataset[[i, var2]]) {
     dataset[[i, merged_var]] <- dataset[[i, var1]]
     dataset[["mismatch"]] <- 0

     # Leftover: var1 != var2
     } else {
       dataset[[i, merged_var]] <- NA
       dataset[["mismatch"]] <- 2  # var1 != var2
     }  # end if
   }  # end for
   return(dataset)
}

ds_var_merge1 <- t_merge_variables(dataset = ds_test,
 var1 = "customer.x",
 var2 = "customer.y",
 merged_var = "customer")

ds_var_merge1

-- cut --

It is executed without error but delivers the wrong values in the variable 
"mismatch". This variable is always 1 although it should be NA, 1 or 2 
respectively.

Can you tell me why the variable is not correctly set?

Kind regards

Georg