sum - Summing Vector elements until a Positive element is encountered - R -

i'm new r , i'm looking through book called "discovering statistics using r". although book implies don't need statistical background, of content isn't covered/explained...

i'm trying sum elements of vector starting position 1 until positive element present.

i found this question similar i'm trying achieve. when implement it, doesn't seem work (and appears include first positive element)...

my program is:

  veca <- runif(10, -10, 10);   suma <-sum(veca [1:min(which(veca < 0))]); 

is there more robust way calculate without using loops works every time , doesn't add positive element? i'm not @ looping stage of books yet.

i found this site asks similar question answer errors:

  sum(veca [seq_len(which.max(veca > 0)]); 

you want use > not < sum elements until first positive 1 reached.

you're summing 1 until first negative value reached (including first negative value).

sum(veca[1:min(which(veca>0))-1]) 

the which() function return of positions of positive elements, taking sum 1 position of first positive - 1 guarantee summing of negative elements