R help - Aug 2006 - locating intervals

Hi ,

I have two sorted vectors X and Xi, where the range of Xi lies within the
range of X.

For an element in Xi, I want to find the neigbouring data in X, e.g. find an
index ix
so that for element number k, then
X[ix[k]] < X[k] < X[ix[k] +1]  # also OK with "<=" on either
one, but not
both

This is easy to code by looping over the data in X,Xi, but I suspect there
may be a faster and more elegant way to do this in R.

In Python (Numeric) the same can be achieved with
ix=Numeric.searchsorted(X[1:-1],Xi),
which is quite compact.

So, does anyone know of a corresponding R  call that can achive the same?

Sincerely,
Halldór

-- 
Halldor Bjornsson
Weatherservice R & D
Icelandic Met. Office

	[[alternative HTML version deleted]]

I'm pretty sure you want to use

findInterval() 

Why did you not find it?
In other words,  what did you try to find it?

Regards,
Martin Maechler, ETH Zurich
>>>>> "halldor" == halldor bjornsson
<halldor.bjornsson at gmail.com>
>>>>>     on Tue, 8 Aug 2006 16:47:18 +0000 writes:
    halldor> Hi , I have two sorted vectors X and Xi, where the
    halldor> range of Xi lies within the range of X.

    halldor> For an element in Xi, I want to find the
    halldor> neigbouring data in X, e.g. find an index ix so
    halldor> that for element number k, then X[ix[k]] < X[k] <
    halldor> X[ix[k] +1] # also OK with "<=" on either one, but
    halldor> not both

    halldor> This is easy to code by looping over the data in
    halldor> X,Xi, but I suspect there may be a faster and more
    halldor> elegant way to do this in R.

    halldor> In Python (Numeric) the same can be achieved with
    halldor> ix=Numeric.searchsorted(X[1:-1],Xi), which is quite
    halldor> compact.

    halldor> So, does anyone know of a corresponding R call that
    halldor> can achive the same?

    halldor> Sincerely, Halld?r

    halldor> -- Halldor Bjornsson Weatherservice R & D Icelandic
    halldor> Met. Office