在R中使用sprintf函数的帮助

我有以下R代码：

df <- xmlToDataFrame(/Users/usr/Desktop/shares.xml)
df$timeStamp <- strptime(as.character(df$XTimeStamp), "%H:%M:%OS")
df$SharePrice <- as.numeric(as.character(df$SharePrice))
sapply(df, class)
options("digits.secs"=3)
diff <- diff(df$SharePrice)
diff
sink (file="c:/xampp/htdocs/data.xml", type="output",split=FALSE)
cat("<graph caption=\"Share Price Data Wave\" subcaption=\"For Company's Name\"    xAxisName=\"Time\" yAxisMinValue=\"0\" yAxisName=\"Price\" decimalPrecision=\"5\" formatNumberScale=\"0\" numberPrefix=\"\" showNames=\"1\" showValues=\"0\" showAlternateHGridColor=\"1\" AlternateHGridColor=\"ff5904\" divLineColor=\"ff5904\" divLineAlpha=\"20\" alternateHGridAlpha=\"5\">\n")
cat(sprintf("    <set name=\"%s\" value=\"%f\" hoverText = \"The difference from last value = %d\" ></set>\n", df$XTimeStamp, df$SharePrice, diff))

---

df要么去掉
df$XTimeStamp
和
df$SharePrice
的第一个元素，要么添加
NA
作为
diff
的第一个元素

cat(sprintf("    <set name=\"%s\" value=\"%f\" hoverText = \"The difference from last value = %d\" ></set>\n", df$XTimeStamp[-1], df$SharePrice[-1], diff))

cat（sprintf（“\n”，df$XTimeStamp[-1]，df$SharePrice[-1]，diff））

或

cat（sprintf（“\n”，df$XTimeStamp，df$SharePrice，c（NA，diff）））
此外，如果您正在进行大量此类模板填充，请查看CRAN上的“brew”包-与您最初的问题无关，但每当我看到一长串难看的“cat”函数调用时，我就不得不提及它。
diff（a）总是比a少一个元素。因此，方法是在第一个元素中添加NA。
cat(sprintf("    <set name=\"%s\" value=\"%f\" hoverText = \"The difference from last value = %d\" ></set>\n", df$XTimeStamp[-1], df$SharePrice[-1], diff))

cat(sprintf("    <set name=\"%s\" value=\"%f\" hoverText = \"The difference from last value = %d\" ></set>\n", df$XTimeStamp, df$SharePrice, c(NA,diff)))