计算网格中的物种出现

Question

我在R 有大约 500,000 分的美国候鸟物种出现数据。

我试图在这些点上叠加一个网格，然后计算每个网格中出现的次数。计算完计数后，我想将它们引用到网格单元 ID。

在 R 中，我使用了 over() 函数来获取范围图中的点，这是一个 shapefile。

#Read in occurrence data
data=read.csv("data.csv", header=TRUE)
coordinates(data)=c("LONGITUDE","LATITUDE")

#Get shapefile of the species' range map
range=readOGR(".",layer="data")

proj4string(data)=proj4string(range)

#Get points within the range map
inside.range=!is.na(over(data,as(range,"SpatialPolygons")))

上面的工作完全符合我的希望，但没有解决我当前的问题：如何处理SpatialPointsDataFrame 类型的点和栅格的网格。您是否建议对栅格网格进行多边形化，并使用我上面指出的相同方法？或者其他流程会更有效吗？

Answer 1

首先，您的 R 代码不能按所写的那样工作。我建议将其复制粘贴到一个干净的会话中，如果它也为您出错，请更正语法错误或包含附加库，直到它运行为止。

也就是说，我假设您应该以二维数字坐标的data.frame 结束。所以，为了对它们进行分箱和计数，任何这样的数据都可以，所以我冒昧地模拟了这样一个数据集。如果这没有捕捉到您数据的相关方面，请纠正我。

## Skip this line if you are the OP, and substitute the real data instead.
data<-data.frame(LATITUDE=runif(100,1,100),LONGITUDE=runif(100,1,100));

## Add the latitudes and longitudes between which each observation is located
## You can substitute any number of breaks you want. Or, a vector of fixed cutpoints
## LATgrid and LONgrid are going to be factors. With ugly level names.
data$LATgrid<-cut(data$LATITUDE,breaks=10,include.lowest=T);
data$LONgrid<-cut(data$LONGITUDE,breaks=10,include.lowest=T);

## Create a single factor that gives the lat,long of each observation. 
data$IDgrid<-with(data,interaction(LATgrid,LONgrid));

## Now, create another factor based on the above one, with shorter IDs and no empty levels
data$IDNgrid<-factor(data$IDgrid); 
levels(data$IDNgrid)<-seq_along(levels(data$IDNgrid));

## If you want total grid-cell count repeated for each observation falling into that grid cell, do this:
data$count<- ave(data$LATITUDE,data$IDNgrid,FUN=length);
## You could have also used data$LONGITUDE, doesn't matter in this case

## If you want just a table of counts at each grid-cell, do this:
aggregate(data$LATITUDE,data[,c('LATgrid','LONgrid','IDNgrid')],FUN=length);
## I included the LATgrid and LONgrid vectors so there would be some 
## sort of descriptive reference accompanying the anonymous numbers in IDNgrid,
## but only IDNgrid is actually necessary

## If you want a really minimalist table, you could do this:
table(data$IDNgrid);