数据

Question

在列表中，有三个数据帧。首先，我想选择较少行的数据框作为参考框。然后，我想根据与参考数据帧的值之间的最小距离对其他数据帧进行子集设置。这是示例：

数据

a<- data.frame(name=c("a1","a2","a3","a4"), x=c(10,15,59,21),y=c(12,16,20,30))
  b<- data.frame(name=c("b1","b2","b3","b4","b5"), x=c(8,9,2,-1,13),y=c(7,1,5,10,0))
  c<- data.frame(name=c("c1","c2","c3","c4","c5","c6","c7"), x=c(1,5,6,2,3,10,-8),y=c(2,-3,7,4,6,15,8))
  all<- list(a=a,b=b,c=c)

这里选择a作为参考，因为它的nrow = 4。现在我要按如下方式计算距离

a1b1, a1b2, a1b3, a1b4,a1b5     
a2b1, a2b2, a2b3, a2b4,a2b5
a3b1, a3b2, a3b3, a3b4,a3b5
a4b1, a4b2, a4b3, a4b4,a4b5

每行的最小距离是对应的，将被添加到数据帧b的称为sub_b的子集中，如下所示：

预期结果

> sub_b
  name x y
1   b1 8 7
2   b3 2 5
3   b1 8 7
4   b3 2 5

类似地，计算a和c之间的距离，然后根据最小距离计算子集c

＃a1c1，a1c2，a1c3，a1c4，a1c5，a1c6，a1c7
＃a2c1，a2c2，a2c3，a2c4，a2c5，a2c6，a2c7
＃a3c1，a3c2，a3c3，a3c4，a3c5，a3c6，a3c7
＃a4c1，a4c2，a4c3，a4c4，a4c5，a4c6，a4c7

，sub_c数据框应为

＃预期结果

> sub_c
  name x y
1   c3 6 7
2   c5 3 6
3   c3 6 7
4   c5 3 6

最后，新列表为new.all <-列表（a = a，sub_b = sub_b，sub_c = sub_c）

这是我的代码

lessRow<- lapply(all, function(x) nrow(x)) 
  lessRow<- which.min(lessRow)   # set the reference frame 

     A<- matrix(a$x, a$y, ,nrow=4,ncol = 2) # convert data frame to matrices 
     B<- matrix(b$x, b$y, ncol = 2,nrow = 5)
     C<- matrix(c$x, c$y, ncol = 2,nrow = 7)

     library(geosphere)     # compute the distances
     dis.ab<- distm(A, B,distGeo)
     dis.ac<- distm(A, C,distGeo)

# select which points of dataframe b is closest to points a
       minm.ab <- apply(A, 1, function(x) {
        dm <- distm(x, B , fun=distGeo)
        return(which.min(dm))
      }) 
# select which points of dataframe c is closest to points a
       minm.ac<- apply(A, 1, function(x) {
         dm <- distm(x, C , fun=distGeo)
         return(which.min(dm))
       }) 
# subset based on the minmuim distance 
       sub_b<- b[minm.ab,]
       sub_c<- c[minm.ac, ]
# create a new list of new data frames by keeping the reference frame (a) as it is.
       new.all<- list (a=a, sub_b=sub_b, sub_c=sub_c)

问题是当数据帧数大于3时，如何在循环中这样做。

Answer 1

我们可以根据行数将参考数据框和剩余数据框分开。然后计算参考数据帧中每行与其余行之间的距离，并获得最小距离，使用该距离对数据帧中的行进行子集化，并获得数据帧列表。

c(list(ref), output)

组合数据框：

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2020-02-01 01:19:04.463850-0800 360Project004[633:99382] Error loading /var/containers/Bundle/Application/0D37C95B-6B87-4389-B2EA-8BB6584D3253/360Project004.app/Frameworks/UnityFramework.framework/UnityFramework:  dlopen(/var/containers/Bundle/Application/0D37C95B-6B87-4389-B2EA-8BB6584D3253/360Project004.app/Frameworks/UnityFramework.framework/UnityFramework, 265): no suitable image found.  Did find:
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根据R中的某些条件对数据帧进行子集

数据

预期结果

这是我的代码

1 个答案: