英文:
mget vs get unable to understand the difference
问题
我有点困惑mget和get的工作方式
我正在使用lapply来读取多个数据框（df1，df2）并进行操作，但是当我使用get时，对象被读取，但如果我用mget替换它，它不起作用，不知道为什么
我注意到的是，如果我使用get，数据框会在全局环境中搜索并作为数据框读取，但如果我使用mget，那么对象会作为列表读取，因此后续的代码无法正常工作
df1 <- tribble(~City_Name, ~Temp, ~Pres, ~Wind_Hor, ~Wind_Ver, ~S_Moist, ~Temp1, ~Pres1, ~Wind1, ~S_Moist1,'Mi', 27, 1019, 287, 278, 78, 1, 2, 2, 1,'Mi', 28, 1019, 289, 277, 78, 2, 2, 1, 3)df2 <- tribble(~City_Name, ~Temp, ~Pres, ~Wind_Hor, ~Rainf, ~S_Moist, ~Temp1, ~Pres1, ~Wind1, ~S_Moist1,'Mi', 27, 1019, 287, 278, 78, 1, 2, 2, 1,'Mi', 28, 1019, 289, 277, 78, 2, 2, 1, 3)dfs1 <- c('df1', 'df2')var <- c('City_Name', 'Temp', 'Pres', 'Wind_Hor', 'Wind_Ver', 'Rainf', 'S_Moist')lapply(dfs1, \(x) {dfn <- mget(x, envir = .GlobalEnv, inherits = T)dfn[[var[which(is.na(match(var, names(dfn))))]]] <- NAdfn <- dfn %>% select(all_of(var))return(assign(x, dfn, envir = .GlobalEnv))})
英文:
I am little confused with the way the mget and get works
I am using the lapply to read the multiple dataframes (df1, df2) and do the manipulation, however when i use the get the object is read but if i replace it with mget, it does not work, not sure why
what i noticed is that if i use the get the dataframe is searched in the global environment and read as a dataframe, however if I use mget then the object is read as a list due to which the further code does not work
df1 <- tribble(~City_Name, ~Temp, ~Pres, ~Wind_Hor, ~Wind_Ver, ~S_Moist, ~Temp1, ~Pres1, ~Wind1, ~S_Moist1,'Mi', 27, 1019, 287, 278, 78, 1, 2, 2, 1,'Mi', 28, 1019, 289, 277, 78, 2, 2, 1, 3)df2 <- tribble(~City_Name, ~Temp, ~Pres, ~Wind_Hor, ~Rainf, ~S_Moist, ~Temp1, ~Pres1, ~Wind1, ~S_Moist1,'Mi', 27, 1019, 287, 278, 78, 1, 2, 2, 1,'Mi', 28, 1019, 289, 277, 78, 2, 2, 1, 3)dfs1 <- c('df1','df2')var <- c('City_Name', 'Temp', 'Pres' , 'Wind_Hor' , 'Wind_Ver' , 'Rainf' , 'S_Moist')lapply(dfs1, \(x) {dfn <- mget(x, envir = .GlobalEnv, inherits = T)dfn[[var[which(is.na(match(var,names(dfn))))]]] <- NAdfn <- dfn %>% select(all_of(var))return(assign(x,dfn,envir = .GlobalEnv))})
答案1
得分: 3
get 用于查找一个变量并返回存储在变量中的值，而 mget 查找多个变量并将它们返回为一个列表。您试图要做的事情可以简化为：
lapply(mget(dfs1), \(x) `[<-`(x, setdiff(var, names(x)), value = NA)[var]) |>list2env(.GlobalEnv)
df1
一个数据框: 2 × 7
城市名称 温度 压力 水平风 垂直风 降雨 土壤湿度
<chr> <dbl> <dbl> <dbl> <dbl> <lgl> <dbl>
1 Mi 27 1019 287 278 NA 78
2 Mi 28 1019 289 277 NA 78
df2
一个数据框: 2 × 7
城市名称 温度 压力 水平风 垂直风 降雨 土壤湿度
<chr> <dbl> <dbl> <dbl> <lgl> <dbl> <dbl>
1 Mi 27 1019 287 NA 278 78
2 Mi 28 1019 289 NA 277 78
英文:
get is used to find only one variable and return the value stored in the variable, while mget finds multiple variable and returns them in a list. What you are trying to do can be simplified as
lapply(mget(dfs1), \(x) `[<-`(x, setdiff(var, names(x)), value = NA)[var]) |>list2env(.GlobalEnv)df1# A tibble: 2 × 7City_Name Temp Pres Wind_Hor Wind_Ver Rainf S_Moist<chr> <dbl> <dbl> <dbl> <dbl> <lgl> <dbl>1 Mi 27 1019 287 278 NA 782 Mi 28 1019 289 277 NA 78df2# A tibble: 2 × 7City_Name Temp Pres Wind_Hor Wind_Ver Rainf S_Moist<chr> <dbl> <dbl> <dbl> <lgl> <dbl> <dbl>1 Mi 27 1019 287 NA 278 782 Mi 28 1019 289 NA 277 78
答案2
得分: 2
以下是使用mget的解决方案。从帮助页面?get中得到以下信息：
按名称搜索一个对象（get）或零个或多个对象（mget）。
在“Value”部分中：
对于
get，找到的对象。如果没有找到对象，将产生错误。对于
mget，一个对象的命名列表（找到或通过ifnotfound指定）。
suppressPackageStartupMessages(library(tibble))df1 <- tribble(~City_Name, ~Temp, ~Pres, ~Wind_Hor, ~Wind_Ver, ~S_Moist, ~Temp1, ~Pres1, ~Wind1, ~S_Moist1,'Mi', 27, 1019, 287, 278, 78, 1, 2, 2, 1,'Mi', 28, 1019, 289, 277, 78, 2, 2, 1, 3)df2 <- tribble(~City_Name, ~Temp, ~Pres, ~Wind_Hor, ~Rainf, ~S_Moist, ~Temp1, ~Pres1, ~Wind1, ~S_Moist1,'Mi', 27, 1019, 287, 278, 78, 1, 2, 2, 1,'Mi', 28, 1019, 289, 277, 78, 2, 2, 1, 3)dfs1 <- c('df1','df2')var <- c('City_Name', 'Temp', 'Pres' , 'Wind_Hor' , 'Wind_Ver' , 'Rainf' , 'S_Moist')# 使用mget一次获取所有数据集df_list <- mget(dfs1, envir = .GlobalEnv, inherits = TRUE)lapply(df_list, \(x) {icol <- var[!var %in% names(x)]x[icol] <- NAx[var]}) ->list2env(envir = .GlobalEnv)# <environment: R_GlobalEnv>df1# # A tibble: 2 × 7# City_Name Temp Pres Wind_Hor Wind_Ver Rainf S_Moist# <chr> <dbl> <dbl> <dbl> <dbl> <lgl> <dbl># 1 Mi 27 1019 287 278 NA 78# 2 Mi 28 1019 289 277 NA 78df2# # A tibble: 2 × 7# City_Name Temp Pres Wind_Hor Wind_Ver Rainf S_Moist# <chr> <dbl> <dbl> <dbl> <lgl> <dbl> <dbl># 1 Mi 27 1019 287 NA 278 78# 2 Mi 28 1019 289 NA 277 78
创建于2023年7月17日，使用reprex v2.0.2
英文:
Here is a solution with mget.
From the help page ?get:
> Search by name for an object (get) or zero or more objects (mget).
And in section Value:
> For get, the object found. If no object is found an error results.
>
> For mget, a named list of objects (found or specified via ifnotfound).
suppressPackageStartupMessages(library(tibble))df1 <- tribble(~City_Name, ~Temp, ~Pres, ~Wind_Hor, ~Wind_Ver, ~S_Moist, ~Temp1, ~Pres1, ~Wind1, ~S_Moist1,'Mi', 27, 1019, 287, 278, 78, 1, 2, 2, 1,'Mi', 28, 1019, 289, 277, 78, 2, 2, 1, 3)df2 <- tribble(~City_Name, ~Temp, ~Pres, ~Wind_Hor, ~Rainf, ~S_Moist, ~Temp1, ~Pres1, ~Wind1, ~S_Moist1,'Mi', 27, 1019, 287, 278, 78, 1, 2, 2, 1,'Mi', 28, 1019, 289, 277, 78, 2, 2, 1, 3)dfs1 <- c('df1','df2')var <- c('City_Name', 'Temp', 'Pres' , 'Wind_Hor' , 'Wind_Ver' , 'Rainf' , 'S_Moist')# get all data sets in one call to mgetdf_list <- mget(dfs1, envir = .GlobalEnv, inherits = TRUE)lapply(df_list, \(x) {icol <- var[!var %in% names(x)]x[icol] <- NAx[var]}) |>list2env(envir = .GlobalEnv)#> <environment: R_GlobalEnv>df1#> # A tibble: 2 × 7#> City_Name Temp Pres Wind_Hor Wind_Ver Rainf S_Moist#> <chr> <dbl> <dbl> <dbl> <dbl> <lgl> <dbl>#> 1 Mi 27 1019 287 278 NA 78#> 2 Mi 28 1019 289 277 NA 78df2#> # A tibble: 2 × 7#> City_Name Temp Pres Wind_Hor Wind_Ver Rainf S_Moist#> <chr> <dbl> <dbl> <dbl> <lgl> <dbl> <dbl>#> 1 Mi 27 1019 287 NA 278 78#> 2 Mi 28 1019 289 NA 277 78
<sup>Created on 2023-07-17 with reprex v2.0.2</sup>
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