Rilcon42 - 1 year ago 54

R Question

I am trying to figure out how to count the number of rows from when one column says True to when the other column says True. I attempted to use run length encoding but couldnt figure out how to get the alternating values form each column.

`set.seed(42)`

s<-sample(c(0,1,2,3),500,replace=T)

isOverbought<-s==1

isOverSold<-s==0

head(cbind(isOverbought,isOverSold),20)

res<-rle(isOverSold)

tt<-res[res$values==0] #getting when Oversold is true

> head(cbind(isOverbought,isOverSold))

[1,] FALSE FALSE

[2,] FALSE FALSE

[3,] TRUE FALSE <-starting condition is overbought

[4,] FALSE FALSE

[5,] FALSE FALSE

[6,] FALSE FALSE

[7,] FALSE FALSE

[8,] FALSE TRUE <-is oversold. length from overbought to oversold = 5

[9,] FALSE FALSE

[10,] FALSE FALSE

[11,] TRUE FALSE <- is overbought. length from oversold to overbought = 3

[12,] FALSE FALSE

[13,] FALSE FALSE

[14,] TRUE FALSE

[15,] TRUE FALSE

[16,] FALSE FALSE

[17,] FALSE FALSE

[18,] FALSE TRUE <-is oversold. length from overbought to oversold = 7

[19,] TRUE FALSE <- is overbought. length from oversold to overbought = 1

[20,] FALSE FALSE

GOAL

`overboughtTOoversold oversoldTOoverbought`

5 3

7 1

Answer Source

This is sufficient to solve your problem.

```
## `a` to `b`
a2b <- function (a, b) {
x <- which(a) ## position of `TRUE` in `a`
y <- which(b) ## position of `TRUE` in `b`
z <- which(a | b) ## position of all `TRUE`
end <- match(y, z) ## match for end position
start <- c(1L, end[-length(end)] + 1L) ## start position
valid <- end > start ## remove cases with `end = start`
z[end[valid]] - z[start[valid]]
}
## cross `a` and `b`
axb <- function (a, b) {
if (any(a & b))
stop ("Invalid input! `a` and `b` can't have TRUE at the same time!")
x <- a2b(a, b); y <- a2b(b, a)
if (which(a)[1L] < which(b)[1L]) cbind(a2b = x, b2a = c(NA_integer_, y))
else cbind(a2b = c(NA_integer_, x), b2a = y)
}
```

For your `isOverbought`

and `isOverSold`

, we obtain:

```
result <- axb(isOverbought, isOverSold)
head(result)
# a2b b2a
#[1,] 5 NA
#[2,] 7 3
#[3,] 3 1
#[4,] 8 5
#[5,] 2 6
#[6,] 10 2
```

Since `isOverbought`

has the first `TRUE`

before `isOverSold`

, the first element of the 2nd column is `NA`

.