Subsetting neighboring fileds

问题

I am trying to make a conditional subsetting which would include contemporary elements inside window of neighboring areas. For example, given the matrix Dat, where Species (SP), Area (AR) and Time (TM):

SP AR TM
A  2  2
B  2  2
C  1  4
F  3  2
B  5  3
E  3  2
D  2  1
I  1  4
H  3  2
E  2  4
D  3  5
B  1  2

How can I retrieve all the species co-occurring with species A in the same time, but within neighboring areas (in this case 1 and 3)? The desired output being:

SP  AR  TM
A  2  2
B  2  2
F  3  2
H  3  2
B  1  2

This is based on the assumption that Species A will be occurring repeatedly in the dataset in different areas. I have an attempt, given by user thelatemail from a different question (with related elements) I posted previously, with minor modifications. The X's added, indicate the part of the syntax I cannot figure out, which would basically be the definition of the bracket (given this is more or less where it should be going).

with(dat,dat[
  apply(
    sapply(TM[SP=="A"],
    function(x) abs(AR)XXXXX),1,any
  )
,]
)

Any help is much appreciated.

This is part of a set of operations I am trying to make on a large dataset. I broke the question into two elements, which are somewhat related but far from being duplicates. The reason for this being I am a beginning R user and want to learn how to interpret, write and integrate codes on my own. The link to the related question: Subsetting based on co-occurrence within a time window . I can remove one of the links if needed.

回答1:

Assuming neighboring areas are defined by areas within +/- 1 of the given area:

Copying from the previous question: Subsetting based on co-occurrence within a time window ...

with(dat,dat[
  (
    SP=="A" |
    # Area %in% Area[SP=="A"]
    Area %in% c(Area[SP=='A']-1, Area[SP=='A'], Area[SP=='A']+1)
  ) & 
  apply(
    sapply(Time[SP=="A"],
    function(x) abs(difftime(Time,x,units="mins"))<=30 ),1,any
  ) 
,]
)

---

As per the comment (and my comment)

area <- 2
dat[dat$AR %in% c(area - 1, area, area + 1),]

---

And in Regards to Conditional subsetting by POSIXct interval and another field containing interval removing the conditional for SP=='A' should result in correct subsetting

area_boolean <- with(dat, Area %in% c(Area[SP=='A']-1, Area[SP=='A'], Area[SP=='A']+1))
time_boolean <- with(dat, apply(sapply(Time[SP=="A"],
                                function(x) abs(difftime(Time, x, units="mins")) <= 30 ),  
                                1, 
                                any))
dat[area_boolean & time_boolean,]

来源：https://stackoverflow.com/questions/18706182/subsetting-neighboring-fileds