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首页 > 解决方案 > FUN(X[[i]], ...) 中的错误：使用 st_polygon 时 is.numeric(x) 不是 TRUE

r - FUN(X[[i]], ...) 中的错误：使用 st_polygon 时 is.numeric(x) 不是 TRUE

问题描述

这从坐标建立在这个线程多边形上

我有一个数据框canopy_coords

> dput(canopy_coords)
structure(list(Transect_ID = c("A", "B", "C", "D", "E", "F", 
"G", "H", "I", "J", "K"), percentage = c(0.141663114074618, 0.679361716844141, 
0.356075131567195, 0.0369279244914651, 0.545912720728666, 0.256667358567938, 
0.887708339374512, 0.355368616292253, 0.0197559630032629, 0.0667797913774848, 
0.513462982373312), pt1_rbx = c(864943.815781996, 864953.870790847, 
864962.2814157, 864970.487301377, 864980.271109795, 864991.027427403, 
865000.351992635, 865008.532059795, 865017.232489794, 865026.778973778, 
865031.926178827), pt1_rby = c(4173793.09292455, 4173792.95070282, 
4173793.68917041, 4173794.85743131, 4173794.84731682, 4173794.94912696, 
4173796.92544687, 4173800.28061334, 4173803.77056191, 4173807.13103388, 
4173809.1564907), pt2_rbx = c(864938.438652263, 864943.815781996, 
864953.870790847, 864962.2814157, 864970.487301377, 864980.271109795, 
864991.027427403, 865000.351992635, 865008.532059795, 865017.232489794, 
865026.778973778), pt2_rby = c(4173793.46951521, 4173793.09292455, 
4173792.95070282, 4173793.68917041, 4173794.85743131, 4173794.84731682, 
4173794.94912696, 4173796.92544687, 4173800.28061334, 4173803.77056191, 
4173807.13103388), pt3_lbx = c(864938.754229696, 864944.008063806, 
864954.103848622, 864962.954663805, 864971.586264863, 864980.897890762, 
864991.945752488, 865002.172447518, 865010.506388562, 865018.820648425, 
865028.048200056), pt3_lby = c(4173789.72813409, 4173789.63976124, 
4173788.97486369, 4173789.15990521, 4173790.60336356, 4173791.370514, 
4173791.58086304, 4173793.66042772, 4173797.6375251, 4173801.15880759, 
4173804.0296625), pt4_lbx = c(864944.008063806, 864954.103848622, 
864962.954663805, 864971.586264863, 864980.897890762, 864991.945752488, 
865002.172447518, 865010.506388562, 865018.820648425, 865028.048200056, 
865033.427710242), pt4_lby = c(4173789.63976124, 4173788.97486369, 
4173789.15990521, 4173790.60336356, 4173791.370514, 4173791.58086304, 
4173793.66042772, 4173797.6375251, 4173801.15880759, 4173804.0296625, 
4173805.40185838)), class = c("tbl_df", "tbl", "data.frame"), row.names = c(NA, 
-11L))

我尝试使用上述线程将其转换为多边形：

polys <- lapply(1:11, function(x){
      # build a matrix of coordinates that enclose the polygon
      pmat <- matrix(c(canopy_coords[x, 'pt1_rby'], canopy_coords[x, 'pt1_rbx'],
                       canopy_coords[x, 'pt2_rby'], canopy_coords[x, 'pt2_rbx'],
                       canopy_coords[x, 'pt3_lby'], canopy_coords[x, 'pt3_lbx'],
                       canopy_coords[x, 'pt4_lby'], canopy_coords[x, 'pt4_lbx'],
                       canopy_coords[x, 'pt1_rby'], canopy_coords[x, 'pt1_rbx']),
                     ncol = 2, byrow = TRUE)
      
      ## create polygon objects
      st_polygon(list(pmat), dim = "XY")
    })

不幸的是，这会产生这个错误：Error in FUN(X[[i]], ...) : is.numeric(x) is not TRUE

当我检查 pmat 时，结构看起来是正确的：

> pmat
     [,1]    [,2]    
[1,] 4173793 864943.8
[2,] 4173793 864938.4
[3,] 4173790 864938.8
[4,] 4173790 864944  
[5,] 4173793 864943.8

如果我“注释”出 st_polygon() 函数，则 polys 对象看起来是正确的：

> head(polys,5)
[[1]]
     [,1]    [,2]    
[1,] 4173793 864943.8
[2,] 4173793 864938.4
[3,] 4173790 864938.8
[4,] 4173790 864944  
[5,] 4173793 864943.8

[[2]]
     [,1]    [,2]    
[1,] 4173793 864953.9
[2,] 4173793 864943.8
[3,] 4173790 864944  
[4,] 4173789 864954.1
[5,] 4173793 864953.9

[[3]]
     [,1]    [,2]    
[1,] 4173794 864962.3
[2,] 4173793 864953.9
[3,] 4173789 864954.1
[4,] 4173789 864963  
[5,] 4173794 864962.3

[[4]]
     [,1]    [,2]    
[1,] 4173795 864970.5
[2,] 4173794 864962.3
[3,] 4173789 864963  
[4,] 4173791 864971.6
[5,] 4173795 864970.5

[[5]]
     [,1]    [,2]    
[1,] 4173795 864980.3
[2,] 4173795 864970.5
[3,] 4173791 864971.6
[4,] 4173791 864980.9
[5,] 4173795 864980.3

寻找任何可以解释正在发生的事情的帮助。

标签： rlapplysf

解决方案

这是因为您的对象canopy_coords不仅仅是 a data.frame，它也是 a tbl。

你可以做两件事：

pmat <- matrix(unlist(c(canopy_coords[x, 'pt1_rby'], canopy_coords[x, 'pt1_rbx'],
                       canopy_coords[x, 'pt2_rby'], canopy_coords[x, 'pt2_rbx'],
                       canopy_coords[x, 'pt3_lby'], canopy_coords[x, 'pt3_lbx'],
                       canopy_coords[x, 'pt4_lby'], canopy_coords[x, 'pt4_lbx'],
                       canopy_coords[x, 'pt1_rby'], canopy_coords[x, 'pt1_rbx'])),
                     ncol = 2, byrow = TRUE)

或者

class(canopy_coords) <- 'data.frame'

其余的保持不变。

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