Shambhavi Srivastava - 4 months ago 29

R Question

In R, I want my while loop to continue until each element in a particular vector 'theta_diff' (which is updated in the while loop in each iteration) reduces below a particular threshold 'epsilon'.

Presently I am able to achieve this by using an OR condition in the while loop test condition (theta_diff is a 2-element vector):

`while((theta_diff[1]>epsilon)|(theta_diff[2]>epsilon))`

{

}

I am wondering if there is a smarter way to do this? I tried the all() but it implements a AND logic instead of an OR logic and so even if one of the theta_diff elements meet the criteria, the while loop stops.

`while(all(theta_diff>epsilon))`

{

}

Main inspiration to search for a smarter option is that: depending upon the program, the dimension of the theta_diff vector may change and I want to make the while loop condition independent of the length of the theta_diff vector.

Answer

I could come up with two options (at least one element of `theta_diff`

is greater than `epsilon`

):

`any(theta_diff > epsilon)`

`max(theta_diff) > epsilon`

Similarly, the following two are equivalent (all elements of `theta_diff`

are greater than `epsilon`

):

`all(theta_diff > epsilon)`

`min(theta_diff) > epsilon`

Sometimes using `repeat`

is more readable than using `while`

. Why not consider:

```
repeat {
## blablabla
if (all(theta_diff > epsilon)) break
}
```

which means ** do ... until ...**.