R: Set a value for certain data meeting two conditions

Question

I don't know how to set this the easiest way. I have a dataframe called Test, with a column containing some NA values. Now I want to set a value of 1 to all fields meeting the following conditions:

1. row number > 60
2. if there is an NA in the specific field

So far I have:

Test$MyColumn[is.na(Test$MyColumn)] <- 1

This works, but I don't know how to set the second condition :-/

Answer 1

If both conditions must apply before you change an element to 1 in bb here is an alternative:

aa <- 1:10
bb <- c(1,NA,6,4,NA,9,1,NA,2,5)
cc <- c(100,102,104,NA,78,54,99,NA,22,0)
dd <- data.frame(aa,bb,cc)
dd
dd$bb[4:nrow(dd)][is.na(dd$bb[4:nrow(dd)])] <- 1
dd

Here is the original data set:

   aa bb  cc
1   1  1 100
2   2 NA 102
3   3  6 104
4   4  4  NA
5   5 NA  78
6   6  9  54
7   7  1  99
8   8 NA  NA
9   9  2  22
10 10  5   0

Here is the modified data set:

   aa bb  cc
1   1  1 100
2   2 NA 102
3   3  6 104
4   4  4  NA
5   5  1  78
6   6  9  54
7   7  1  99
8   8  1  NA
9   9  2  22
10 10  5   0

This changes NA in rows 4-10 of all columns if there is an NA in rows 4-10 of bb:

aa <- 1:10
bb <- c(1,NA,6,4,NA,9,1,NA,2,5)
cc <- c(100,102,104,NA,78,54,99,NA,22,0)
dd <- data.frame(aa,bb,cc)
dd
dd[4:nrow(dd),1:3][is.na(dd$bb[4:nrow(dd)]),] <- 1
dd

   aa bb  cc
1   1  1 100
2   2 NA 102
3   3  6 104
4   4  4  NA
5   1  1   1
6   6  9  54
7   7  1  99
8   1  1   1
9   9  2  22
10 10  5   0

This changes NA in rows 4-10 of all columns if there is an NA in rows 4-10 of bb then it changes all remaining NA in bb:

aa <- 1:10
bb <- c(1,NA,6,4,NA,9,1,NA,2,5)
cc <- c(100,102,104,NA,78,54,99,NA,22,0)
dd <- data.frame(aa,bb,cc)
dd
dd[4:nrow(dd),1:3][is.na(dd$bb[4:nrow(dd)]),] <- 1
dd$bb[is.na(dd$bb)] <- 1
dd

   aa bb  cc
1   1  1 100
2   2  1 102
3   3  6 104
4   4  4  NA
5   1  1   1
6   6  9  54
7   7  1  99
8   1  1   1
9   9  2  22
10 10  5   0