CODEWITHSUNDEEP
rlapply
Alberson Miranda
Alberson Miranda

Reputation: 1430

lapply: vector names as list names

When using lapply() over a vector, each element of the resulting list doesn't have a name, but only an index:

library(dplyr)

vector = c("df1", "df2")

df1 = data.frame(a = rnorm(5), b = rnorm(5, sd = 1.1))
df2 = data.frame(a = rnorm(5), b = rnorm(5, sd = 1.1))

lapply(vector, function(x){
  
  x = get(x) %>%
    mutate(c = a+b)
})
#> [[1]]
#>            a          b          c
#> 1 -0.4098768  1.6712810  1.2614041
#> 2  0.7101722 -0.1025184  0.6076538
#> 3 -0.6696859  0.5690932 -0.1005928
#> 4  1.1642214 -0.4660378  0.6981836
#> 5 -0.5158280  1.4574039  0.9415759
#> 
#> [[2]]
#>             a         b          c
#> 1  0.91047848 -1.308707 -0.3982281
#> 2  1.87336493 -1.429567  0.4437977
#> 3  0.54171333  1.849589  2.3913028
#> 4 -0.02978158  2.500763  2.4709817
#> 5  1.49926589  1.602463  3.1017284

It does has names when applying over list:

list = list(
  df1 = data.frame(a = rnorm(5), b = rnorm(5, sd = 1.1)),
  df2 = data.frame(a = rnorm(5), b = rnorm(5, sd = 1.1))
)

lapply(list, function(x){
  
  x = x %>%
    mutate(c = a+b)
})
#> $df1
#>            a          b           c
#> 1  0.8228400 -2.5232496 -1.70040963
#> 2  0.3890213 -0.4349408 -0.04591949
#> 3  0.5084719  1.4089123  1.91738415
#> 4  0.2533964 -0.7379615 -0.48456516
#> 5 -0.2474338  1.0520906  0.80465685
#> 
#> $df2
#>            a           b          c
#> 1  0.1376350 -1.32304077 -1.1854058
#> 2  0.1314702  1.14775210  1.2792223
#> 3  0.9757047 -1.24806193 -0.2723573
#> 4 -0.5118045  0.09277009 -0.4190344
#> 5 -0.1631715 -0.47573087 -0.6389024

Is there a simple way to use the vector elements as the resulting list names?

Upvotes: 1

Views: 97

Answers (3)

akrun
akrun

Reputation: 887851

We can also use map

library(purrr)
library(dplyr)
map(mget(vector), ~ .x %>%
                        mutate(c = a + b))

Upvotes: 0

Wimpel
Wimpel

Reputation: 27802

You could name the vector, before lapply

vector = c("df1", "df2")
names(vector) <- vector  # <-- here

df1 = data.frame(a = rnorm(5), b = rnorm(5, sd = 1.1))
df2 = data.frame(a = rnorm(5), b = rnorm(5, sd = 1.1))


lapply(vector, function(x){

    x = get(x) %>%
    mutate(c = a+b)
})

# $df1
# a          b          c
# 1 -0.36671838  0.8733203  0.5066019
# 2 -0.05029296 -0.8823471 -0.9326401
# 3  0.54252815 -0.2087211  0.3338071
# 4 -1.16789527  0.2598863 -0.9080090
# 5 -0.80664672 -0.4968422 -1.3034889
# 
# $df2
# a          b          c
# 1  0.9042845  1.2978663  2.2021508
# 2 -0.3848533 -0.4563623 -0.8412156
# 3 -1.1681873  1.3224087  0.1542215
# 4  1.4872564 -2.0281272 -0.5408708
# 5 -0.2717229 -0.3780464 -0.6497694

Upvotes: 2

Ronak Shah
Ronak Shah

Reputation: 389235

Instead of using get on each list separately, you can use mget to get all the dataframes in a list with their names :

lapply(mget(vector), function(x) transform(x, c = a + b))

#$df1
#            a         b          c
#1 -0.60421251 2.4792735  1.8750610
#2  0.06163947 2.0295196  2.0911590
#3 -0.56318825 2.1496891  1.5865009
#4 -2.46292843 1.1641211 -1.2988073
#5 -1.05692446 0.4365812 -0.6203432

#$df2
#            a         b         c
#1 -0.33388039 0.6690467 0.3351663
#2  0.83637236 1.3321715 2.1685439
#3  0.05839826 0.1017032 0.1601015
#4 -0.20686296 0.8667050 0.6598420
#5  0.52682053 0.4629632 0.9897837

Upvotes: 3

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