add hard test analysis

output/hard/README.md

@@ -0,0 +1,215 @@
+Hard Test Analysis
+================
+
+## Introduction
+
+The hard test pushes the **boundaries** of XML parsing with the xml2
+package, focusing on the **conversion** of an XML document into a
+**structured R list**. This test not only tests the package’s parsing
+capabilities but also its ability to **transform** XML data into a
+format that is easily manipulable within R. It involves creating a
+**custom** **function** to recursively parse the XML document,
+demonstrating the xml2 package’s flexibility and power in handling
+complex XML structures. The code snippet in this section provides a
+comprehensive example of how to leverage the xml2 package to parse XML
+documents into R lists, showcasing the package’s robustness and
+versatility in XML data manipulation.
+
+### <u>Section 1: Loading Libraries and XML Content</u>
+
+``` r
+library(xml2)
+library(stringr)
+library(rlist)
+
+z <- '
+<CATALOG>
+ <CD>
+    <TITLE>Empire Burlesque</TITLE>
+    <ARTIST>Bob Dylan</ARTIST>
+    <COUNTRY>USA</COUNTRY>
+    <COMPANY>Columbia</COMPANY>
+    <PRICE>10.90</PRICE>
+    <YEAR>1985</YEAR>
+ </CD>
+ <CD>
+    <TITLE>Hide your heart</TITLE>
+    <ARTIST>Bonnie Tylor</ARTIST>
+    <COUNTRY>UK</COUNTRY>
+    <COMPANY>CBS Records</COMPANY>
+    <PRICE>9.90</PRICE>
+    <YEAR>1988</YEAR>
+ </CD>
+</CATALOG>'
+```
+
+**Explanation**
+
+- The **xml2, stringr**, and **rlist** libraries are loaded to handle
+  XML data and list manipulation in R.
+
+- An XML content string representing a **catalog** of **CDs** is
+  defined, including details like title, artist, country, company,
+  price, and year.
+
+### <u>Section 2: Parsing XML to List Using rlist</u>
+
+``` r
+res <- rlist::list.parse(z, type='xml')
+res
+```
+
+    ## $CD
+    ## $CD$TITLE
+    ## [1] "Empire Burlesque"
+    ## 
+    ## $CD$ARTIST
+    ## [1] "Bob Dylan"
+    ## 
+    ## $CD$COUNTRY
+    ## [1] "USA"
+    ## 
+    ## $CD$COMPANY
+    ## [1] "Columbia"
+    ## 
+    ## $CD$PRICE
+    ## [1] "10.90"
+    ## 
+    ## $CD$YEAR
+    ## [1] "1985"
+    ## 
+    ## 
+    ## $CD
+    ## $CD$TITLE
+    ## [1] "Hide your heart"
+    ## 
+    ## $CD$ARTIST
+    ## [1] "Bonnie Tylor"
+    ## 
+    ## $CD$COUNTRY
+    ## [1] "UK"
+    ## 
+    ## $CD$COMPANY
+    ## [1] "CBS Records"
+    ## 
+    ## $CD$PRICE
+    ## [1] "9.90"
+    ## 
+    ## $CD$YEAR
+    ## [1] "1988"
+
+**Explanation**
+
+- The **list.parse** function from the rlist package is used to parse
+  the XML string into an R list.
+
+- The **type=‘xml’** argument specifies that the input is XML content.
+
+- The **parsed list** is stored in the variable res.
+
+### <u>Section 3: Custom Function to Parse XML to List</u>
+
+``` r
+parse_xml_to_list <- function(xml_string) {
+ xml_doc <- read_xml(xml_string)
+
+ xml_to_list <- function(node) {
+
+    if (xml_length(node) == 0) {
+      return(xml_text(node))
+    } 
+
+    else {
+      children <- xml_children(node)
+      list_result <- lapply(children, xml_to_list)
+      return(setNames(list_result, xml_name(children)))
+    }
+ }
+
+ result <- xml_to_list(xml_doc)
+
+ return(result)
+}
+```
+
+**Explanation**
+
+- A custom function **parse_xml_to_list** is defined to parse an XML
+  string into an R list.
+
+- The function uses **recursion** to **traverse** the **XML document**.
+  If a node has no children, it returns the text content of the node.
+  Otherwise, it creates a list with the node’s name as the key and the
+  **children’s list** as the value.
+
+- The **xml_length** function is used to check if a node has children.
+
+- The **xml_children** function is used to get the children of a node.
+
+- The **xml_name** function is used to get the name of a node.
+
+- The **xml_text** function is used to get the text content of a node.
+
+### <u>Section 4: Using the Custom Function</u>
+
+``` r
+res2 <- parse_xml_to_list(z)
+
+print(res2)
+```
+
+    ## $CD
+    ## $CD$TITLE
+    ## [1] "Empire Burlesque"
+    ## 
+    ## $CD$ARTIST
+    ## [1] "Bob Dylan"
+    ## 
+    ## $CD$COUNTRY
+    ## [1] "USA"
+    ## 
+    ## $CD$COMPANY
+    ## [1] "Columbia"
+    ## 
+    ## $CD$PRICE
+    ## [1] "10.90"
+    ## 
+    ## $CD$YEAR
+    ## [1] "1985"
+    ## 
+    ## 
+    ## $CD
+    ## $CD$TITLE
+    ## [1] "Hide your heart"
+    ## 
+    ## $CD$ARTIST
+    ## [1] "Bonnie Tylor"
+    ## 
+    ## $CD$COUNTRY
+    ## [1] "UK"
+    ## 
+    ## $CD$COMPANY
+    ## [1] "CBS Records"
+    ## 
+    ## $CD$PRICE
+    ## [1] "9.90"
+    ## 
+    ## $CD$YEAR
+    ## [1] "1988"
+
+``` r
+identical(res, res2) 
+```
+
+    ## [1] TRUE
+
+**Explanation**
+
+- The custom function **parse_xml_to_list** is used to parse the XML
+  string z into an R list, which is stored in res2.
+
+- The **print** function is used to display the parsed list.
+
+- The **identical** function checks if the list parsed by
+  **rlist::list.parse** is identical to the list parsed by the custom
+  function, demonstrating the equivalence of the two methods.

output/hard/analysis.Rmd

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+---
+title: "Hard Test Analysis"
+output: github_document
+---
+
+## Introduction
+
+The hard test pushes the **boundaries** of XML parsing with the xml2 package, focusing on the **conversion** of an XML document into a **structured R list**. This test not only tests the package's parsing capabilities but also its ability to **transform** XML data into a format that is easily manipulable within R. It involves creating a **custom** **function** to recursively parse the XML document, demonstrating the xml2 package's flexibility and power in handling complex XML structures. The code snippet in this section provides a comprehensive example of how to leverage the xml2 package to parse XML documents into R lists, showcasing the package's robustness and versatility in XML data manipulation.
+
+### [Section 1: Loading Libraries and XML Content]{.underline}
+
+```{r message=FALSE}
+
+library(xml2)
+library(stringr)
+library(rlist)
+
+z <- '
+<CATALOG>
+ <CD>
+    <TITLE>Empire Burlesque</TITLE>
+    <ARTIST>Bob Dylan</ARTIST>
+    <COUNTRY>USA</COUNTRY>
+    <COMPANY>Columbia</COMPANY>
+    <PRICE>10.90</PRICE>
+    <YEAR>1985</YEAR>
+ </CD>
+ <CD>
+    <TITLE>Hide your heart</TITLE>
+    <ARTIST>Bonnie Tylor</ARTIST>
+    <COUNTRY>UK</COUNTRY>
+    <COMPANY>CBS Records</COMPANY>
+    <PRICE>9.90</PRICE>
+    <YEAR>1988</YEAR>
+ </CD>
+</CATALOG>'
+```
+
+**Explanation**
+
+-   The **xml2, stringr**, and **rlist** libraries are loaded to handle XML data and list manipulation in R.
+
+-   An XML content string representing a **catalog** of **CDs** is defined, including details like title, artist, country, company, price, and year.
+
+### [Section 2: Parsing XML to List Using rlist]{.underline}
+
+```{r message=FALSE}
+
+res <- rlist::list.parse(z, type='xml')
+res
+```
+
+**Explanation**
+
+-   The **list.parse** function from the rlist package is used to parse the XML string into an R list.
+
+-   The **type='xml'** argument specifies that the input is XML content.
+
+-   The **parsed list** is stored in the variable res.
+
+### [Section 3: Custom Function to Parse XML to List]{.underline}
+
+```{r message=FALSE}
+
+parse_xml_to_list <- function(xml_string) {
+ xml_doc <- read_xml(xml_string)
+  
+ xml_to_list <- function(node) {
+    
+    if (xml_length(node) == 0) {
+      return(xml_text(node))
+    } 
+    
+    else {
+      children <- xml_children(node)
+      list_result <- lapply(children, xml_to_list)
+      return(setNames(list_result, xml_name(children)))
+    }
+ }
+    
+ result <- xml_to_list(xml_doc)
+  
+ return(result)
+}
+```
+
+**Explanation**
+
+-   A custom function **parse_xml_to_list** is defined to parse an XML string into an R list.
+
+-   The function uses **recursion** to **traverse** the **XML document**. If a node has no children, it returns the text content of the node. Otherwise, it creates a list with the node's name as the key and the **children's list** as the value.
+
+-   The **xml_length** function is used to check if a node has children.
+
+-   The **xml_children** function is used to get the children of a node.
+
+-   The **xml_name** function is used to get the name of a node.
+
+-   The **xml_text** function is used to get the text content of a node.
+
+### [Section 4: Using the Custom Function]{.underline}
+
+```{r message=FALSE}
+
+res2 <- parse_xml_to_list(z)
+
+print(res2)
+
+identical(res, res2) 
+```
+
+**Explanation**
+
+-   The custom function **parse_xml_to_list** is used to parse the XML string z into an R list, which is stored in res2.
+
+-   The **print** function is used to display the parsed list.
+
+-   The **identical** function checks if the list parsed by **rlist::list.parse** is identical to the list parsed by the custom function, demonstrating the equivalence of the two methods.