I tried to paste the variable and concatenate with the remaining column name but it always returns an error. Plus, I think I am making it unnecessarily hard running though various for loops and retroactively renaming rows.

In principle, I'd like to make a row-wise subtraction of the value in the `DELY_QTY` column from all `WK_DIFF_XX` values individually and write the result in a new column `DIFF_XX`, whereby XX corresponds with the digit of the `WK_DIFF` column.

```
> str(df_full)
'data.frame':   959 obs. of  18 variables:
 $ DELY_DATE : Date, format: "2015-01-26" "2015-02-02" "2015-02-09" "2015-02-16" ...
 $ WK_DIFF_3 : int  37 40 72 30 41 36 63 28 19 8 ...
 $ WK_DIFF_4 : int  NA 40 72 31 44 35 57 28 19 6 ...
 $ WK_DIFF_5 : int  NA NA 73 35 43 33 57 27 24 6 ...
 $ WK_DIFF_6 : int  NA NA NA 37 48 35 57 27 31 14 ...
 $ WK_DIFF_7 : int  NA NA NA NA 52 39 49 39 39 25 ...
 $ WK_DIFF_8 : int  NA NA NA NA NA 47 53 41 36 25 ...
 $ WK_DIFF_9 : int  NA NA NA NA NA NA 51 42 34 30 ...
 $ WK_DIFF_10: int  NA NA NA NA NA NA NA 43 35 30 ...
 $ WK_DIFF_11: int  NA NA NA NA NA NA NA NA 35 30 ...
 $ WK_DIFF_12: int  NA NA NA NA NA NA NA NA NA 30 ...
 $ WK_DIFF_13: int  NA NA NA NA NA NA NA NA NA NA ...
 $ WK_DIFF_14: int  NA NA NA NA NA NA NA NA NA NA ...
 $ WK_DIFF_15: int  NA NA NA NA NA NA NA NA NA NA ...
 $ WK_DIFF_16: int  NA NA NA NA NA NA NA NA NA NA ...
 $ WK_DIFF_17: int  NA NA NA NA NA NA NA NA NA NA ...
 $ WK_DIFF_18: int  NA NA NA NA NA NA NA NA NA NA ...
 $ DELY_QTY  : int  82 62 57 57 67 57 53 70 70 60 ...

```

Although it looks that some of the `WK_DIFF` columns are empty they contain values further down the bottom of the column.

```
> dput(df_full[1:5, ])
structure(list(DELY_DATE = structure(c(16461, 16468, 16475, 16482, 
16489), class = "Date"), WK_DIFF_3 = c(37L, 40L, 72L, 30L, 41L
), WK_DIFF_4 = c(NA, 40L, 72L, 31L, 44L), WK_DIFF_5 = c(NA, NA, 
73L, 35L, 43L), WK_DIFF_6 = c(NA, NA, NA, 37L, 48L), WK_DIFF_7 = c(NA, 
NA, NA, NA, 52L), WK_DIFF_8 = c(NA_integer_, NA_integer_, NA_integer_, 
NA_integer_, NA_integer_), WK_DIFF_9 = c(NA_integer_, NA_integer_, 
NA_integer_, NA_integer_, NA_integer_), WK_DIFF_10 = c(NA_integer_, 
NA_integer_, NA_integer_, NA_integer_, NA_integer_), WK_DIFF_11 = c(NA_integer_, 
NA_integer_, NA_integer_, NA_integer_, NA_integer_), WK_DIFF_12 = c(NA_integer_, 
NA_integer_, NA_integer_, NA_integer_, NA_integer_), WK_DIFF_13 = c(NA_integer_, 
NA_integer_, NA_integer_, NA_integer_, NA_integer_), WK_DIFF_14 = c(NA_integer_, 
NA_integer_, NA_integer_, NA_integer_, NA_integer_), WK_DIFF_15 = c(NA_integer_, 
NA_integer_, NA_integer_, NA_integer_, NA_integer_), WK_DIFF_16 = c(NA_integer_, 
NA_integer_, NA_integer_, NA_integer_, NA_integer_), WK_DIFF_17 = c(NA_integer_, 
NA_integer_, NA_integer_, NA_integer_, NA_integer_), WK_DIFF_18 = c(NA_integer_, 
NA_integer_, NA_integer_, NA_integer_, NA_integer_), DELY_QTY = c(82L, 
62L, 57L, 57L, 67L)), row.names = c(NA, 5L), class = "data.frame")

```

I appreciate the suggestion for the proper approach to this.