如何用子串

Question

我想用substring（）编辑多个列名。只有我写的代码不起作用。

奇怪的是，以下代码有效。 旧列名：

oldColNames <- names(forcesdf[,c(5:20)])

结果：

> names(forcesdf[,c(5:20)])
[1] "2000 [YR2000]" "2001 [YR2001]" "2002 [YR2002]" "2003 [YR2003]" "2004 [YR2004]" "2005 [YR2005]" "2006 [YR2006]"
[8] "2007 [YR2007]" "2008 [YR2008]" "2009 [YR2009]" "2010 [YR2010]" "2011 [YR2011]" "2012 [YR2012]" "2013 [YR2013]"
[15] "2014 [YR2014]" "2015 [YR2015]"

新列名称：

newColNames <- substring(names(forcesdf[,c(5:20)]), 1, 4)
oldColNames <- newColNames

结果出乎我想要的那样：

> oldColNames
[1] "2000" "2001" "2002" "2003" "2004" "2005" "2006" "2007" "2008" "2009" "2010" "2011" "2012" "2013" "2014" "2015"

当然，我想更改数据框中的列名，所以最初，我编写了以下代码，但代码名没有改变。

names(forcesdf[,c(5:20)]) <- substring(names(forcesdf[,c(5:20)]), 1, 4)

> names(forcesdf[,c(5:20)])
[1] "2000 [YR2000]" "2001 [YR2001]" "2002 [YR2002]" "2003 [YR2003]" "2004 [YR2004]" "2005 [YR2005]" "2006 [YR2006]"
[8] "2007 [YR2007]" "2008 [YR2008]" "2009 [YR2009]" "2010 [YR2010]" "2011 [YR2011]" "2012 [YR2012]" "2013 [YR2013]"
[15] "2014 [YR2014]" "2015 [YR2015]"

Answer 1

测试此

names(forcesdf)[5:20] <- substring(names(forcesdf[,c(5:20)]), 1, 4)

Answer 2

如果您这样做，可以更改它们：

names(forcesdf)[5:20] <- substring(names(forcesdf)[5:20], 1, 4)

我认为关键是你的代码中你是列名列的子集，但没有引用它们。