Ernie - 9 months ago 60

R Question

I want to build a matrix or data frame by choosing names of columns where the element in the data frame contains does not contain an NA. For example, suppose I have:

`zz <- data.frame(a = c(1, NA, 3, 5),`

b = c(NA, 5, 4, NA),

c = c(5, 6, NA, 8))

which gives:

`a b c`

1 1 NA 5

2 NA 5 6

3 3 4 NA

4 5 NA 8

I want to recognize each NA and build a new matrix or df that looks like:

`a c`

b c

a b

a c

There will be the same number of NAs in each row of the input matrix/df. I can't seem to get the right code to do this. Suggestions appreciated!

Answer

```
library(dplyr)
library(tidyr)
zz %>%
mutate(k = row_number()) %>%
gather(column, value, a, b, c) %>%
filter(!is.na(value)) %>%
group_by(k) %>%
summarise(temp_var = paste(column, collapse = " ")) %>%
separate(temp_var, into = c("var1", "var2"))
# A tibble: 4 × 3
k var1 var2
* <int> <chr> <chr>
1 1 a c
2 2 b c
3 3 a b
4 4 a c
```

Source (Stackoverflow)