Xml 是否允许用户选择要分析的数据文件的范围？

我有以下XML文件：

<Company >
    <shareprice>
        <timeStamp> 12:00:00.01</timeStamp>
        <Price>  25.02</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:00.02</timeStamp>
        <Price>  15</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:01.025</timeStamp>
        <Price>  15.02</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:01.031</timeStamp>
        <Price>  18.25</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:01.039</timeStamp>
        <Price>  18.54</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:01.050</timeStamp>
        <Price> 16.52</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:02.01</timeStamp>
        <Price>  17.50</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:03.01</timeStamp>
        <Price>  25.02</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:05.02</timeStamp>
        <Price>  30</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:11.025</timeStamp>
        <Price>  32.25</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:12.031</timeStamp>
        <Price>  26.05</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:15.039</timeStamp>
        <Price>  18.54</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:00:19.050</timeStamp>
        <Price> 16.52</Price>
    </shareprice>

    <shareprice>
        <timeStamp> 12:01:02.01</timeStamp>
        <Price>  17.50</Price>
    </shareprice>
</Company>

12:00:00.01
25.02
12:00:00.02
15
12:00:01.025
15.02
12:00:01.031
18.25
12:00:01.039
18.54
12:00:01.050
16.52
12:00:02.01
17.50
12:00:03.01
25.02
12:00:05.02
30
12:00:11.025
32.25
12:00:12.031
26.05
12:00:15.039
18.54
12:00:19.050
16.52
12:01:02.01
17.50

我还有以下R代码：

library (ggplot2)
library (XML)
df <- xmlToDataFrame(file.choose()) 
df$timeStamp <- strptime(as.character(df$timeStamp), "%H:%M:%OS")
df$Price <- as.numeric(as.character(df$Price))
sapply(df, class)          
options("digits.secs"=3)   
summary (df)              
df$timeStamp <- df[1,"timeStamp"] + cumsum(runif(1:length(df$timeStamp))*60)
summary(df)
diff1 = 0
diff <- append(diff1,diff(df$Price))
summary (df$Price)
Ymin <- min(df$Price)
Ymax <- max(df$Price)
Ymedian <- median (df$Price)
Ymean <- mean(df$Price)
Ysd <- sd (df$Price)
sink (file="c:/xampp/htdocs/Sharedata.xml", type="output",split=FALSE)
cat("<graph caption=\"Share Data Wave\" subcaption=\"For Person's Name\"   xAxisName=\"Time\" yAxisMinValue=\"-0.025\" yAxisName=\"Voltage\" decimalPrecision=\"5\"  formatNumberScale=\"0\" numberPrefix=\"\" showNames=\"1\" showValues=\"0\" showAlternateHGridColor=\"1\" AlternateHGridColor=\"ff5904\" divLineColor=\"ff5904\" divLineAlpha=\"20\" alternateHGridAlpha=\"5\">\n")
cat(sprintf("    <set name=\"%s\" value=\"%f\" hoverText = \"The difference from last value: %s\" ></set>\n", df$timeStamp, df$Price, diff))
cat ("</graph>\n")
unlink("data.xml")
sink (file="c:/xampp/htdocs/Sharesstatistics.xml", type="output",split=FALSE)
cat ("  <statistics>\n")
cat (sprintf("    <mean>%s</mean>\n", Ymean))
cat (sprintf("    <sd>%s</sd>\n",Ysd))
cat (sprintf("    <min>%s</min>\n", Ymin))
cat (sprintf("    <median>%s</median>\n",Ymedian))
cat (sprintf("    <max>%s</max>\n", Ymax))
cat ("  </statistics>\n")
unlink("statistics.xml")
quit()

库（ggplot2）
库（XML）
df只要读取数据帧，然后要求用户使用eg scan（n=2）给出记录的上下限，就可以很容易地解决这个问题。另请参见？扫描。它允许您以交互方式提供输入，因此用户可以选择要执行的操作。这是输入要使用的数据范围的情况

x <- scan(n=2)
id <- min(x):max(x)

df2 <- df[id,]

x
x <- scan(n=2)
id <- min(x):max(x)

df2 <- df[id,]

# function reads a subset of an xml file,
# assuming a white line is dividing the individual records.
# n is a vector containing the record numbers wanted

subset.xml <- function(x,n,...){
    # set a range if n is just a number
    if (length(n)==1) n <- 1:n

    #initiate vars
    skp <- 0 # the number of lines to skip by scan
    count <- 1
    out <- character(1)

  repeat{
      tmp <- scan(x,what=character(0),n=1,skip=skp,blank.lines.skip=F,sep="\n")
      skp <- skp+1
      if(length(tmp)==0) {break} # no more input

      if((count %in% n) & (tmp !="")) out <- paste(out,tmp,sep="\n")
      if(tmp=="") count <- count+1 # white line seperates records
  }
  out <- substring(out,3)
  out <- paste("<Data>",out,"</Data>",sep="\n")
  return(xmlToDataFrame(xmlParse(out)))
}

df <- subset.xml("test.xml",2:4)
> df
      timeStamp   Price
1   12:00:00.02      15
2  12:00:01.025   15.02
3  12:00:01.031   18.25