Dear David,
The toy example doesn't represent functions as such, but represents type of
data that I'm operating with. These data are product of an analysis. If I
understand you correctly, I would need to approximate distribution functions of
these data first and then integrate. This makes sense, but any suggestion/ideas
of how to do it in R?
Many thanks!
Best regards,
Ana
>________________________________
>From: David Winsemius <dwinsem...@comcast.net>
>To: Ana Kolar <annako...@yahoo.com>
>Cc: R <r-help@r-project.org>
>Sent: Monday, 18 July 2011, 16:41
>Subject: Re: [R] SDMTools package - calculating overlap?
>
>
>On Jul 18, 2011, at 10:11 AM, Ana Kolar wrote:
>
>> Yes, indeed! I believe I should integrate differences of min of both
>> functions, no? I'm not quite sure how this should be done in R therefore I
>> was wondering if there are some build in functions that do this job already.
>> If not I would appreciate any help of how should it be done otherwise.
>
>?integrate # would seem to be the glaringly obvious help query
>
>>
>> Toy example of data is here:
>>
>> a <- matrix(runif(30))
>> b <- matrix(runif(30))
>
>That's not a well-defined example of functions even if we take the index to be
>the x value. Presumably you have some sort of value in mind for "a" at an
>x-value of 1.5 but it is not clear from what you have presented.
>
>?stepfun
>?approxfun
>
>
>A function takes inputs (on some continuous measurement scale) and returns
>results. Perhaps you should be seeking some local mathematical/statistical
>consulting resource.
>
>--David.
>
>>
>> I tried to calculate this overlap with "Istat" function but am not sure that
>> it does the job right! This is the example:
>>
>> library(SDMTools)
>> a <- matrix(runif(30))
>> b <- matrix(runif(30))
>> Istat(a,b)
>>
>> Many thanks for your response, David!
>>
>> Ana
>>
>>
>>
>> From: David Winsemius <dwinsem...@comcast.net>
>> To: Ana Kolar <annako...@yahoo.com>
>> Cc: R <r-help@r-project.org>
>> Sent: Monday, 18 July 2011, 15:45
>> Subject: Re: [R] SDMTools package - calculating overlap?
>>
>>
>> On Jul 18, 2011, at 9:40 AM, Ana Kolar wrote:
>>
>> > Dear R users,
>> >
>> > Any idea of how to calculate an area of an overlap between two functions?
>> > The only R build in function that I found is I Similarity Statistic for
>> > Quantifying Niche Overlap and I am really not sure if this function is
>> > producing exactly what I am interested in since I was plotting functions
>> > and often got confused results (for example: got high value for the
>> > overlap of one pair and low for the other pair, while from the plot it
>> > looked like the first pair was overlapping better.) Can anyone please
>> > explain what's the reason behind such a behaviour? And does anyone has a
>> > suggestion of what function could be used for a calculation of an overlap
>> > area? The problem with 'Istat' function is also that it requires both data
>> > sets to have the same length, while I would be more interested in a
>> > function that enables overlap calculation even if data sets have different
>> > length. Looking forward to hearing from you! Have a good day. Ana
>>
>> Shouldn't you be integrating their difference (or the absolute value of
>> their differences depending on your definition of "overlap"). I fail in
>> understanding your example. Where is/are the function(s)?
>>
>> >
>> > library(SDMTools)
>> > a <- matrix(runif(30))
>> > b <- matrix(runif(30))
>> > Istat(a,b)
>> > [[alternative HTML version deleted]]
>> --
>> David Winsemius, MD
>> West Hartford, CT
>>
>>
>>
>
>David Winsemius, MD
>West Hartford, CT
>
>
>
>
[[alternative HTML version deleted]]
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