R-从环境中的多个变量获取值

我当前的R环境中有一些变量：

ls()
 [1] "clt.list"      "commands.list" "dirs.list"     "eq"            "hurs.list"     "mlist"         "prec.list"     "temp.list"     "vars"         
[10] "vars.list"     "wind.list"    

其中，变量“clt.list”、“hurs.list”、“prec.list”、“temp.list”和“wind.list”中的每一个都是一个（巨大的）字符串列表

例如：

clt.list[1:20]
 [1] "clt_Amon_ACCESS1-0_historical_r1i1p1_185001-200512.nc"        "clt_Amon_ACCESS1-3_historical_r1i1p1_185001-200512.nc"       
 [3] "clt_Amon_bcc-csm1-1_historical_r1i1p1_185001-201212.nc"       "clt_Amon_bcc-csm1-1-m_historical_r1i1p1_185001-201212.nc"    
 [5] "clt_Amon_BNU-ESM_historical_r1i1p1_185001-200512.nc"          "clt_Amon_CanESM2_historical_r1i1p1_185001-200512.nc"         
 [7] "clt_Amon_CCSM4_historical_r1i1p1_185001-200512.nc"            "clt_Amon_CESM1-BGC_historical_r1i1p1_185001-200512.nc"       
 [9] "clt_Amon_CESM1-CAM5_historical_r1i1p1_185001-200512.nc"       "clt_Amon_CESM1-CAM5-1-FV2_historical_r1i1p1_185001-200512.nc"
[11] "clt_Amon_CESM1-FASTCHEM_historical_r1i1p1_185001-200512.nc"   "clt_Amon_CESM1-WACCM_historical_r1i1p1_185001-200512.nc"     
[13] "clt_Amon_CMCC-CESM_historical_r1i1p1_190001-190412.nc"        "clt_Amon_CMCC-CESM_historical_r1i1p1_190001-200512.nc"       
[15] "clt_Amon_CMCC-CESM_historical_r1i1p1_190501-190912.nc"        "clt_Amon_CMCC-CESM_historical_r1i1p1_191001-191412.nc"       
[17] "clt_Amon_CMCC-CESM_historical_r1i1p1_191501-191912.nc"        "clt_Amon_CMCC-CESM_historical_r1i1p1_192001-192412.nc"       
[19] "clt_Amon_CMCC-CESM_historical_r1i1p1_192501-192912.nc"        "clt_Amon_CMCC-CESM_historical_r1i1p1_193001-193412.nc" 

var.names <- c("clt.list", "commands.list", "dirs.list")

我需要做的是提取介于“Amon_”和“_historical”之间的字符串子集

我可以对单个变量执行此操作，如下所示：

levels(as.factor(sub(".*?Amon_(.*?)_historical.*", "\\1", clt.list[1:20])))
 [1] "ACCESS1-0"        "ACCESS1-3"        "bcc-csm1-1"       "bcc-csm1-1-m"     "BNU-ESM"          "CanESM2"          "CCSM4"           
 [8] "CESM1-BGC"        "CESM1-CAM5"       "CESM1-CAM5-1-FV2" "CESM1-FASTCHEM"   "CESM1-WACCM"      "CMCC-CESM"

然而，我想做的是同时为所有五个变量运行上面的命令。在上面的命令中，我不只是使用“ctl.list”作为参数，而是同时使用所有变量“clt.list”、“hurs.list”、“prec.list”、“temp.list”和“wind.list”

我该怎么做

---

非常感谢

一种解决方案是创建一个包含要从中提取数据的变量名的向量，例如：

clt.list[1:20]
 [1] "clt_Amon_ACCESS1-0_historical_r1i1p1_185001-200512.nc"        "clt_Amon_ACCESS1-3_historical_r1i1p1_185001-200512.nc"       
 [3] "clt_Amon_bcc-csm1-1_historical_r1i1p1_185001-201212.nc"       "clt_Amon_bcc-csm1-1-m_historical_r1i1p1_185001-201212.nc"    
 [5] "clt_Amon_BNU-ESM_historical_r1i1p1_185001-200512.nc"          "clt_Amon_CanESM2_historical_r1i1p1_185001-200512.nc"         
 [7] "clt_Amon_CCSM4_historical_r1i1p1_185001-200512.nc"            "clt_Amon_CESM1-BGC_historical_r1i1p1_185001-200512.nc"       
 [9] "clt_Amon_CESM1-CAM5_historical_r1i1p1_185001-200512.nc"       "clt_Amon_CESM1-CAM5-1-FV2_historical_r1i1p1_185001-200512.nc"
[11] "clt_Amon_CESM1-FASTCHEM_historical_r1i1p1_185001-200512.nc"   "clt_Amon_CESM1-WACCM_historical_r1i1p1_185001-200512.nc"     
[13] "clt_Amon_CMCC-CESM_historical_r1i1p1_190001-190412.nc"        "clt_Amon_CMCC-CESM_historical_r1i1p1_190001-200512.nc"       
[15] "clt_Amon_CMCC-CESM_historical_r1i1p1_190501-190912.nc"        "clt_Amon_CMCC-CESM_historical_r1i1p1_191001-191412.nc"       
[17] "clt_Amon_CMCC-CESM_historical_r1i1p1_191501-191912.nc"        "clt_Amon_CMCC-CESM_historical_r1i1p1_192001-192412.nc"       
[19] "clt_Amon_CMCC-CESM_historical_r1i1p1_192501-192912.nc"        "clt_Amon_CMCC-CESM_historical_r1i1p1_193001-193412.nc" 

var.names <- c("clt.list", "commands.list", "dirs.list")

---

var.names您可以将操作放入函数中，然后对其进行迭代：

get_my_substr <- function(vecname) 
  levels(as.factor(sub(".*?Amon_(.*?)_historical.*", "\\1", get(vecname))))

lapply(my_vecnames,get_my_substr)



在你的问题中张贴一个可复制的例子通常是一种好的做法。因为这里没有提供，所以我用

# example-maker
prestr <- "grr_Amon_"
posstr <- "_historical_zzz"
make_ex <- function() 
  replicate(
    sample(10,1),
    paste0(prestr,paste0(sample(LETTERS,sample(5,1)),collapse=""),posstr)
  )

# make a couple examples
set.seed(1)
m01 <- make_ex()
m02 <- make_ex()

# test result
lapply(ls(pattern="^m[0-9][0-9]$"),get_my_substr)

#示例生成器
“谢谢你的建议，@Richard Ambler。不过我还是希望避免循环。谢谢@Frank。这个函数正是我想要的。另外，我更喜欢lappy命令，因为它避免了循环。