You could use a combination of "match" and "trim" to do the job
But this line will fail if no negative values are present
so we will use "onerror" (in Prime you would use "try") to catch that error and return the vector unchanged
But there is still a situation, where we will get unwanted results. If ALL values in the vector are negative, nothing will be left. This throws an error and because errors are trapped by "onerror" now we get back the original vector, which is not the desired behavior.
So I thought that now its time to write an utility function to do the job and call later when needed (I have chosen to return NaN in the last case, change as appropriate)
Hope this helps
Werner
For completeness sake here the Prime version
The basic line (first one in my answer above) will work in Prime Express, too, but for the error catching you need the full version because "try" is a programming command and programming is considered a premium feature which is not enabled in the free Express variant.
EDIT: Just found that the "trim" command is also considered a premium feature, so not even the basic line won't work in Express 
And just for fun here is an alternative, classic approach, going through the vector element by element and collecting the appropriate elements for the new, trimmed vector
WE
