[R-sig-Geo] How to count unique TRUE's

[Robert J. Hijmans]

Forrest, it seems to me that you can simplify and do

output$AC[i] <- length(gIntersection(tmp, ac))

instead of

tmp2 <- as.vector(gIntersects(tmp, ac, byid=TRUE))
output$AC[i] <- length(tmp[tmp2 == TRUE])

Robert

On Tue, Mar 31, 2015 at 11:56 AM, Forrest Stevens <forrest at ufl.edu> wrote:
> I'm guessing based on the data and situation you describe that some
> variant of this would probably get you close:
>
>
> ##  Sample data:
> d <- data.frame(A=c(T,F,F,T), B=c(F,T,F,T))
>
> ##  Count row-wise trues:
> sum( apply(d, MARGIN=1, sum) >= 1 )
>
>
> Hope that helps,
> Forrest
> --
> Forrest R. Stevens
> Ph.D. Candidate, QSE3 IGERT Fellow
> Department of Geography
> Land Use and Environmental Change Institute
> University of Florida
> www.clas.ufl.edu/users/forrest
>
>
> On Tue, Mar 31, 2015 at 2:29 PM, Tom Philippi <tephilippi at gmail.com> wrote:
>> I can't quite make sense of what your objects look like, but I suspect you
>> need to change byid to a vector, so you are byid for the points but not the
>> polygons byid=c(FALSE,TRUE) or vice versa.
>>
>>
>> On Tue, Mar 31, 2015 at 10:55 AM, Walter Anderson <wandrson01 at gmail.com>
>> wrote:
>>
>>> I have a buffered project SpatialPolygonDataFrame and a
>>> SpatialPointDataFrame that I want to intersect (one project at a time)
>>> and count the number of points within each polygon's footprint.
>>>
>>> I am using the following code:
>>>
>>> for (i in 1:numprjs)
>>> {
>>>         curprj <- as.character(output at PROJECT[i])
>>>         tmp <- subset(buf2640, buf2640$PROJECT == curprj)
>>>         tmp2 <- as.vector(gIntersects(tmp, ac, byid=TRUE))
>>>         output$AC[i] <- length(tmp[tmp2 == TRUE])
>>> }
>>>
>>> The problem is that when the project's polygons cover more than one
>>> overlapping shapes (derived from multiple sub-projects that are given
>>> the same project id), the above code can multiple count a single ac
>>> point if it falls within the boundaries of two or more of a single
>>> projects polygons.
>>>
>>> As an example project 'B1103' has two points within its two polygons;
>>> however, the above code reports three.  I believe the following extract
>>> of the core gIntersects command shows why
>>>
>>>         2     3
>>> 122 FALSE  TRUE
>>> 313  TRUE  TRUE
>>>
>>> So clearly the problem is my use of as.vector, which is taking all of
>>> the columns and combining them into a single vector; however, I am
>>> unsure of the best way to count the number of true in the original data
>>> structure created by the gIntersects command.
>>>
>>> Walter Anderson
>>>
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>>> R-sig-Geo at r-project.org
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>>>
>>
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