Question

I’m working with the following example:

Original     Modified     New_Orig     New
1            2            1            0
2            4            1            0
3            6            4            0
4            8            5            0
5            10           5            0
6            12           5            0
7            14           5            0
8            16           5            0
9            18           9            0
10           20           10           0

I want to replace values in New with values from Modified if New_Orig matches with any value in Original.

Ideally New will look like this:

New
2  
2
8
10
10
10
10
10
18
20  

Any help much appreciated.

Kind regards,

Answer 1

Here, a new column New is created:

within(dat, New <- Modified*(New_Orig == Original))

   Original Modified New_Orig New
1         1        2        1   2
2         2        4        1   0
3         3        6        4   0
4         4        8        5   0
5         5       10        5  10
6         6       12        5   0
7         7       14        5   0
8         8       16        5   0
9         9       18        9  18
10       10       20       10  20

Update

Match values and choose appropriate value from Modified:

within(dat, New <- Modified[match(New_Orig, Original)])

   Original Modified New_Orig New
1         1        2        1   2
2         2        4        1   2
3         3        6        4   8
4         4        8        5  10
5         5       10        5  10
6         6       12        5  10
7         7       14        5  10
8         8       16        5  10
9         9       18        9  18
10       10       20       10  20