如何解决传递空参数作为数组索引
我有一个函数，它接受用户输入的数组索引，然后执行计算。索引必须是字符串。这是上下文的数据属性的一个片段：
> attributes(data)
$dim
[1] 50 100 100
$dimnames
$dimnames[[1]]
[1] "0.001" "0.613224489795918" "1.22544897959184" "1.83767346938775" "2.44989795918367" "3.06212244897959"
[7] "3.67434693877551" "4.28657142857143" "4.89879591836735" "5.51102040816327" "6.12324489795918" "6.7354693877551"
[13] "7.34769387755102" "7.95991836734694" "8.57214285714286" "9.18436734693877" "9.79659183673469" "10.4088163265306"
[19] "11.0210408163265" "11.6332653061224" "12.2454897959184" "12.8577142857143" "13.4699387755102" "14.0821632653061"
[25] "14.694387755102" "15.306612244898" "15.9188367346939" "16.5310612244898" "17.1432857142857" "17.7555102040816"
[31] "18.3677346938776" "18.9799591836735" "19.5921836734694" "20.2044081632653" "20.8166326530612" "21.4288571428571"
[37] "22.0410816326531" "22.653306122449" "23.2655306122449" "23.8777551020408" "24.4899795918367" "25.1022040816327"
[43] "25.7144285714286" "26.3266530612245" "26.9388775510204" "27.5511020408163" "28.1633265306122" "28.7755510204082"
[49] "29.3877755102041" "30"
$dimnames[[2]]
[1] "10" "20" "30" "40" "50" "60" "70" "80" "90" "100" "110" "120" "130" "140" "150" "160" "170" "180"
[19] "190" "200" "210" "220" "230" "240" "250" "260" "270" "280" "290" "300" "310" "320" "330" "340" "350" "360"
[37] "370" "380" "390" "400" "410" "420" "430" "440" "450" "460" "470" "480" "490" "500" "510" "520" "530" "540"
[55] "550" "560" "570" "580" "590" "600" "610" "620" "630" "640" "650" "660" "670" "680" "690" "700" "710" "720"
[73] "730" "740" "750" "760" "770" "780" "790" "800" "810" "820" "830" "840" "850" "860" "870" "880" "890" "900"
[91] "910" "920" "930" "940" "950" "960" "970" "980" "990" "1000"
$dimnames[[3]]
[1] "1" "2" "3" "4" "5" "6" "7" "8" "9" "10" "11" "12" "13" "14" "15" "16" "17" "18" "19" "20" "21"
[22] "22" "23" "24" "25" "26" "27" "28" "29" "30" "31" "32" "33" "34" "35" "36" "37" "38" "39" "40" "41" "42"
[43] "43" "44" "45" "46" "47" "48" "49" "50" "51" "52" "53" "54" "55" "56" "57" "58" "59" "60" "61" "62" "63"
[64] "64" "65" "66" "67" "68" "69" "70" "71" "72" "73" "74" "75" "76" "77" "78" "79" "80" "81" "82" "83" "84"
[85] "85" "86" "87" "88" "89" "90" "91" "92" "93" "94" "95" "96" "97" "98" "99" "100"
我想要这样的东西：
myfun <- function(index){
apply(X=data[,index,],MARGIN = c(1,2),FUN = mean)
}
但是，如果用户要选择整个数据集，则需要具有data[,]。但是，由于不能将空参数传递给函数，因此我不确定如何实现此目的。如何将逗号之间的空白点表示为函数参数？
解决方法
您可以使用missing，以便缺少索引意味着“全选”，我认为这意味着用户只想要总体平均值。
myfun <- function(index)
{
if(missing(index)) mean(data) else apply(data[,index,],1:2,mean)
}