在R中应用函数后如何保留数据帧结构？
当我们使用Apply系列应用函数时，默认情况下，输出不是以数据框的形式。如果要保留原始数据帧结构，则需要设置apply系列的应用程序，方法是将其设置为带有单个方括号且不带参数的原始数据帧，如以下示例所示。
例1
考虑以下数据帧-
> df1<-data.frame(x1=rpois(20,5),x2=rpois(20,2)) > df1输出结果
x1 x2 1 4 2 2 6 2 3 5 2 4 2 1 5 8 4 6 7 2 7 5 3 8 5 1 9 4 2 10 6 1 11 5 2 12 6 1 13 3 2 14 2 4 15 7 2 16 6 1 17 8 2 18 3 5 19 6 3 20 5 2
将具有lapply的功能粘贴应用于df1-
> lapply(df1, function(x) paste(x,"%",sep=""))输出结果
$x1 [1] "4%" "6%" "5%" "2%" "8%" "7%" "5%" "5%" "4%" "6%" "5%" "6%" "3%" "2%" "7%" [16] "6%" "8%" "3%" "6%" "5%" $x2 [1] "2%" "2%" "2%" "1%" "4%" "2%" "3%" "1%" "2%" "1%" "2%" "1%" "2%" "4%" "2%" [16] "1%" "2%" "5%" "3%" "2%"
将具有lapply的功能粘贴应用于df1并保留数据帧结构-
> df1[]<-lapply(df1, function(x) paste(x,"%", sep="")) > df1输出结果
x1 x2 1 4% 2% 2 6% 2% 3 5% 2% 4 2% 1% 5 8% 4% 6 7% 2% 7 5% 3% 8 5% 1% 9 4% 2% 10 6% 1% 11 5% 2% 12 6% 1% 13 3% 2% 14 2% 4% 15 7% 2% 16 6% 1% 17 8% 2% 18 3% 5% 19 6% 3% 20 5% 2%
例2
> df2<-data.frame(y1=rnorm(20),y2=rnorm(20)) > df2输出结果
y1 y2 1 -0.752047670 1.13712713 2 -0.128263190 -0.32853561 3 -0.302105388 0.13927555 4 -0.962792837 -0.11345683 5 -0.792733177 -0.44710830 6 -0.374832959 -0.11577915 7 0.006232538 1.69377281 8 -0.248837346 1.53856740 9 -1.329142492 -0.93981148 10 -0.800394342 0.23268426 11 -0.024673008 -1.45167348 12 -0.798652443 0.56592880 13 0.752464819 0.26117631 14 0.356222254 1.09788129 15 -0.189963724 0.04015303 16 1.237747888 0.30426806 17 -0.079703224 -1.19632730 18 0.610445704 -0.09226399 19 1.312108743 0.59445517 20 0.117974479 0.31822741
将具有lapply的功能粘贴应用于df2-
> lapply(df2, function(x) paste(x,"*100",sep=""))输出结果
$y1 [1] "-0.75204767044446*100" "-0.128263189709441*100" [3] "-0.302105388264774*100" "-0.962792837263563*100" [5] "-0.792733176975126*100" "-0.37483295904029*100" [7] "0.0062325380738995*100" "-0.24883734622218*100" [9] "-1.32914249184804*100" "-0.800394341521099*100" [11] "-0.0246730078659625*100" "-0.798652442767393*100" [13] "0.752464818654371*100" "0.356222253519168*100" [15] "-0.189963724365201*100" "1.23774788828591*100" [17] "-0.0797032238997077*100" "0.61044570354826*100" [19] "1.31210874294046*100" "0.117974478781838*100" $y2 [1] "1.13712713179116*100" "-0.328535609444004*100" [3] "0.139275554888166*100" "-0.113456833535264*100" [5] "-0.447108300367073*100" "-0.115779145719786*100" [7] "1.69377280937111*100" "1.53856740099674*100" [9] "-0.939811483903564*100" "0.232684264342039*100" [11] "-1.45167347644544*100" "0.565928797260725*100" [13] "0.261176305488481*100" "1.09788129483035*100" [15] "0.0401530283786003*100" "0.304268061193212*100" [17] "-1.1963272953655*100" "-0.0922639906523411*100" [19] "0.594455172315153*100" "0.318227406098396*100"
将具有lapply的功能粘贴应用于df2并保留数据帧结构-
> df2[]<-lapply(df2, function(x) paste(x,"*100",sep="")) > df2输出结果
y1 y2 1 -0.75204767044446*100 1.13712713179116*100 2 -0.128263189709441*100 -0.328535609444004*100 3 -0.302105388264774*100 0.139275554888166*100 4 -0.962792837263563*100 -0.113456833535264*100 5 -0.792733176975126*100 -0.447108300367073*100 6 -0.37483295904029*100 -0.115779145719786*100 7 0.0062325380738995*100 1.69377280937111*100 8 -0.24883734622218*100 1.53856740099674*100 9 -1.32914249184804*100 -0.939811483903564*100 10 -0.800394341521099*100 0.232684264342039*100 11 -0.0246730078659625*100 -1.45167347644544*100 12 -0.798652442767393*100 0.565928797260725*100 13 0.752464818654371*100 0.261176305488481*100 14 0.356222253519168*100 1.09788129483035*100 15 -0.189963724365201*100 0.0401530283786003*100 16 1.23774788828591*100 0.304268061193212*100 17 -0.0797032238997077*100 -1.1963272953655*100 18 0.61044570354826*100 -0.0922639906523411*100 19 1.31210874294046*100 0.594455172315153*100 20 0.117974478781838*100 0.318227406098396*100