Hi

Step 1: I create a data.frame called iolm.
Step 2: I create a conditional subset i_wtr.
Step 3: In this subset I add 0.3 to all values in the IOLM_AST column.
Step 4: Now I am looking for the best way to Śmergeą the altered subset back
into the original iolm data.frame

## STEP 1
>iolm
     ID IOLM_AST IOLM_AXIS
1     1     1.15    165.33
2     2     1.20     79.00
3     3     0.40     51.66
4     4     0.50     57.00
5     5     1.77      7.70
6     6     0.28     99.70
7     7     0.48    160.00
8     8     0.74     84.00
9     9     1.63     87.00
10   10     0.43    150.70
....

## STEP 2

> i_wtr<-subset(iolm,IOLM_AXIS > 60 & IOLM_AXIS < 120)
> i_wtr
     ID IOLM_AST IOLM_AXIS
2     2     1.20      79.0
6     6     0.28      99.7
8     8     0.74      84.0
9     9     1.63      87.0
16   16     0.93      94.0
20   20     1.37      91.0
21   21     1.19      63.0
...

## STEP 3

i_wtr$IOLM_AST <- i_wtr$IOLM_AST + 0.3
> i_wtr
     ID IOLM_AST IOLM_AXIS
2     2     1.50      79.0
6     6     0.58      99.7
8     8     1.04      84.0
9     9     1.93      87.0
16   16     1.23      94.0
20   20     1.67      91.0
21   21     1.49      63.0
...

## STEP 4 ­ result (not what I wish to get)

newiolm<-merge(i_wtr, iolm, by.x="ID", by.y="ID", all = T)
> newiolm
     ID IOLM_AST.x IOLM_AXIS.x IOLM_AST.y IOLM_AXIS.y
1     1         NA          NA       1.15      165.33
2     2       1.50        79.0       1.20       79.00
3     3         NA          NA       0.40       51.66
4     4         NA          NA       0.50       57.00
5     5         NA          NA       1.77        7.70
6     6       0.58        99.7       0.28       99.70
7     7         NA          NA       0.48      160.00
8     8       1.04        84.0       0.74       84.00
9     9       1.93        87.0       1.63       87.00
10   10         NA          NA       0.43      150.70
...


## The result I am looking to get:

     ID   IOLM_AST   IOLM_AXIS
1     1       1.15      165.33
2     2       1.50       79.00
3     3       0.40       51.66
4     4       0.50       57.00
5     5       1.77       7.70
6     6       0.58       99.70
7     7       0.48       160.00
8     8       1.04       84.00
9     9       1.93       87.00
10   10       0.43       150.70
...

What is the correct way to do this?
Thanks a lot for your help.
Dominik

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