Question

[作业问题]

我正在创建一个S3构造函数/对象/脚本。我的脚本中有一个列表，需要打印如下：

ID: 9876  Name: Virgil  Gender: M
LDL: 248* HDL: 45+  Triglycerides: 148

我之前定义了一个打印功能。

print.ChlorReads <- function(theObject) {
  cat("ID: ", theObject$id, " Name: ", theObject$name, " Gender: ", theObject$gender,
      "\n", "LDL: ", theObject$ldl, " HDL: ", theObject$hdl, " Triglycerides: ", theObject$trigl)
}

如何正确使用该脚本，以便以上面指定的格式打印列表中的每个项目？

我可以通过print（lst）来打印列表，但是，列表看起来像这样：

[[1]]
$id
[1] 1111

$name
[1] "Charlene"

$gender
[1] "F"

$ldl
[1] 111

$hdl
[1] 81

$trigl
[1] 136

attr(,"class")
[1] "Patient"

[[2]]
$id
[1] 2222

$name
[1] "Charles"

$gender
[1] "M"

$ldl
[1] 141

$hdl
[1] 78

$trigl
[1] 123

attr(,"class")
[1] "Patient"

[[3]]
$id
[1] 3333

$name
[1] "Kate"

$gender
[1] "F"

$ldl
[1] 121

$hdl
[1] 63

$trigl
[1] 141

attr(,"class")
[1] "Patient"

[[4]]
$id
[1] 4444

$name
[1] "Alice"

$gender
[1] "F"

$ldl
[1] 97

$hdl
[1] 79

$trigl
[1] 111

attr(,"class")
[1] "Patient"

[[5]]
$id
[1] 5555

$name
[1] "Jason"

$gender
[1] "M"

$ldl
[1] 121

$hdl
[1] 85

$trigl
[1] 123

attr(,"class")
[1] "Patient"

[[6]]
$id
[1] 6666

$name
[1] "Spencer"

$gender
[1] "M"

$ldl
[1] 111

$hdl
[1] 81

$trigl
[1] 127

attr(,"class")
[1] "Patient"

[[7]]
$id
[1] 7777

$name
[1] "Mary"

$gender
[1] "F"

$ldl
[1] 108

$hdl
[1] 86

$trigl
[1] 120

attr(,"class")
[1] "Patient"

[[8]]
$id
[1] 8888

$name
[1] "Jarrod"

$gender
[1] "M"

$ldl
[1] 252

$hdl
[1] 38

$trigl
[1] 411

attr(,"class")
[1] "Patient"

[[9]]
$id
[1] 9999

$name
[1] "Cary"

$gender
[1] "M"

$ldl
[1] 121

$hdl
[1] 47

$trigl
[1] 139

attr(,"class")
[1] "Patient"

[[10]]
$id
[1] 1234

$name
[1] "Michael"

$gender
[1] "M"

$ldl
[1] 123

$hdl
[1] 49

$trigl
[1] 134

attr(,"class")
[1] "Patient"

[[11]]
$id
[1] 2345

$name
[1] "Charlotte"

$gender
[1] "F"

$ldl
[1] 135

$hdl
[1] 69

$trigl
[1] 361

attr(,"class")
[1] "Patient"

[[12]]
$id
[1] 3456

$name
[1] "Blake"

$gender
[1] "F"

$ldl
[1] 95

$hdl
[1] 57

$trigl
[1] 126

attr(,"class")
[1] "Patient"

编辑：这里是dput（lst）的输出，正如评论中所要求的那样：

list(structure(list(id = 1111L, name = "Charlene", gender = "F", 
    ldl = 111L, hdl = 81L, trigl = 136L), .Names = c("id", "name", 
"gender", "ldl", "hdl", "trigl"), class = "Patient"), structure(list(
    id = 2222L, name = "Charles", gender = "M", ldl = 141L, hdl = 78L, 
    trigl = 123L), .Names = c("id", "name", "gender", "ldl", 
"hdl", "trigl"), class = "Patient"), structure(list(id = 3333L, 
    name = "Kate", gender = "F", ldl = 121L, hdl = 63L, trigl = 141L), .Names = c("id", 
"name", "gender", "ldl", "hdl", "trigl"), class = "Patient"), 
    structure(list(id = 4444L, name = "Alice", gender = "F", 
        ldl = 97L, hdl = 79L, trigl = 111L), .Names = c("id", 
    "name", "gender", "ldl", "hdl", "trigl"), class = "Patient"), 
    structure(list(id = 5555L, name = "Jason", gender = "M", 
        ldl = 121L, hdl = 85L, trigl = 123L), .Names = c("id", 
    "name", "gender", "ldl", "hdl", "trigl"), class = "Patient"), 
    structure(list(id = 6666L, name = "Spencer", gender = "M", 
        ldl = 111L, hdl = 81L, trigl = 127L), .Names = c("id", 
    "name", "gender", "ldl", "hdl", "trigl"), class = "Patient"), 
    structure(list(id = 7777L, name = "Mary", gender = "F", ldl = 108L, 
        hdl = 86L, trigl = 120L), .Names = c("id", "name", "gender", 
    "ldl", "hdl", "trigl"), class = "Patient"), structure(list(
        id = 8888L, name = "Jarrod", gender = "M", ldl = 252L, 
        hdl = 38L, trigl = 411L), .Names = c("id", "name", "gender", 
    "ldl", "hdl", "trigl"), class = "Patient"), structure(list(
        id = 9999L, name = "Cary", gender = "M", ldl = 121L, 
        hdl = 47L, trigl = 139L), .Names = c("id", "name", "gender", 
    "ldl", "hdl", "trigl"), class = "Patient"), structure(list(
        id = 1234L, name = "Michael", gender = "M", ldl = 123L, 
        hdl = 49L, trigl = 134L), .Names = c("id", "name", "gender", 
    "ldl", "hdl", "trigl"), class = "Patient"), structure(list(
        id = 2345L, name = "Charlotte", gender = "F", ldl = 135L, 
        hdl = 69L, trigl = 361L), .Names = c("id", "name", "gender", 
    "ldl", "hdl", "trigl"), class = "Patient"), structure(list(
        id = 3456L, name = "Blake", gender = "F", ldl = 95L, 
        hdl = 57L, trigl = 126L), .Names = c("id", "name", "gender", 
    "ldl", "hdl", "trigl"), class = "Patient"))

Answer 1

您可能需要循环遍历作为参数传递的列表的长度。

尝试这个小修改：

print.ChlorReads <- function(theObject) {
for (i in 1:length(theObject)){
  cat("List entry: ", i, "\nID: ", theObject[[i]]$id, " Name: ", theObject[[i]]$name, " Gender: ", theObject[[i]]$gender,
      "\n", "LDL: ", theObject[[i]]$ldl, " HDL: ", theObject[[i]]$hdl, " Triglycerides: ", theObject[[i]]$trigl,"\n")
 }
}

Answer 2

鉴于带有list条目的patient的示例，我们应该使用两种不同的打印方法。一种处理list结构的打印方法，通过将每个元素打印命令分配给处理patient类的另一个元素。

要符合print.*() S3方法 - a.k.a对包提交传递CRAN检查 - 您必须将对象的名称设为x，然后...

# Prints the patient information (one item in the list)
print.Patient = function(x, ...){

  cat("ID: ", x$id, " Name: ", x$name, " Gender: ", x$gender,
      "\nLDL: ", x$ldl, " HDL: ", x$hdl, " Triglycerides: ", x$trigl,"\n", sep="")

}

# Print function defined for list type
print.ChlorReads = function(x, ...) {

  # Process each item in the list
  for(i in seq_along(x)){

     # Call the method to print patient info
     print.Patient(x[[i]]) 

  }
}

现在，您需要做的下一步是将lst的类定义为ChlorReads：

class(lst) = c('ChlorReads', class(lst))

通过class(lst)包含当前类可以回退到通用S3支持的类型。

因此，在找到print语句和开场帖中给出的上述样本对象后，我得到了所需的结果：

class(lst) = c('ChlorReads', class(lst))

print(lst)

这给出了：

ID: 1111 Name: Charlene Gender: F
LDL: 111 HDL: 81 Triglycerides: 136
ID: 2222 Name: Charles Gender: M
LDL: 141 HDL: 78 Triglycerides: 123
ID: 3333 Name: Kate Gender: F
LDL: 121 HDL: 63 Triglycerides: 141
ID: 4444 Name: Alice Gender: F
LDL: 97 HDL: 79 Triglycerides: 111
ID: 5555 Name: Jason Gender: M
LDL: 121 HDL: 85 Triglycerides: 123
ID: 6666 Name: Spencer Gender: M
LDL: 111 HDL: 81 Triglycerides: 127
ID: 7777 Name: Mary Gender: F
LDL: 108 HDL: 86 Triglycerides: 120
ID: 8888 Name: Jarrod Gender: M
LDL: 252 HDL: 38 Triglycerides: 411
ID: 9999 Name: Cary Gender: M
LDL: 121 HDL: 47 Triglycerides: 139
ID: 1234 Name: Michael Gender: M
LDL: 123 HDL: 49 Triglycerides: 134
ID: 2345 Name: Charlotte Gender: F
LDL: 135 HDL: 69 Triglycerides: 361
ID: 3456 Name: Blake Gender: F
LDL: 95 HDL: 57 Triglycerides: 126

如何使用我之前在脚本中定义的打印功能打印列表？

2 个答案: