列出套件個數
##ls：list objcts
##search：找出安裝的套件
##lapply(search(), ls)：列出所有套件
##length：長度、個數
str(lapply(search(), ls))## List of 9
## $ : chr(0)
## $ : chr [1:448] "acf" "acf2AR" "add.scope" "add1" ...
## $ : chr [1:87] "abline" "arrows" "assocplot" "axis" ...
## $ : chr [1:110] "adjustcolor" "as.graphicsAnnot" "as.raster" "axisTicks" ...
## $ : chr [1:245] "?" "adist" "alarm" "apropos" ...
## $ : chr [1:104] "ability.cov" "airmiles" "AirPassengers" "airquality" ...
## $ : chr [1:218] "addNextMethod" "allGenerics" "allNames" "Arith" ...
## $ : chr(0)
## $ : chr [1:1232] "-" "-.Date" "-.POSIXt" "!" ...## [[1]]
## [1] 0
##
## [[2]]
## [1] 448
##
## [[3]]
## [1] 87
##
## [[4]]
## [1] 110
##
## [[5]]
## [1] 245
##
## [[6]]
## [1] 104
##
## [[7]]
## [1] 218
##
## [[8]]
## [1] 0
##
## [[9]]
## [1] 1232