Neil - 1 month ago 7

R Question

I have following dataframe in r

`count1 count2 count3 Count4`

0 12 11 0

12 0 44 23

22 32 0 12

Formula that I want to apply on row wise is like this

`1st row sqrt((count2-count3)^2)`

2nd row sqrt((count1-count3)^2 + (count1-count4)^2 + (count3-count4)^2)

3rd row sqrt((count1-count2)^2 + (count1-count4)^2 + (count2-count4)^2)

I do not want to take columns with zero values into consideration. I have 6 columns like above. How can I do it in r?

Applying for loop and checking for every row for non zero elements is tedious task.

Answer Source

Using:

```
apply(df, 1, function(x) {
y <- x[x!=0]
yc <- combn(y,2)
sqrt(sum(apply(yc, 2, function(x) (x[1] - x[2])^2)))
})
```

gives:

`[1] 1.00000 39.82462 24.49490 776.72389`

You can shorten this to:

```
apply(df, 1, function(x) {
sqrt(sum(apply(combn(x[x!=0],2), 2, function(x) (x[1] - x[2])^2)))
})
```

Used data:

```
df <- structure(list(count1 = c(0L, 12L, 22L, 160L), count2 = c(12L, 0L, 32L, 621L),
count3 = c(11L, 44L, 0L, 573L), count4 = c(0L, 23L, 12L, 624L)),
.Names = c("count1", "count2", "count3", "count4"), class = "data.frame", row.names = c(NA, -4L))
```

which looks like:

`> df count1 count2 count3 count4 1 0 12 11 0 2 12 0 44 23 3 22 32 0 12 4 160 621 573 624`