CODEWITHSUNDEEP
rdplyrlapply
user7353167
user7353167

Reputation:

Filter values in multiple dataframes

I can not get my head around this. I have a dataset which contains a data.frame in per day for 3 years, so i have a list with 1000 dataframes.

I want to filter all dataframes like in the example below. I know I could easily filter (or use rbindlist), first and then do the split, but I desire a way to apply a filter function to multiple dataframes. Can you help me? The code below does not work, but hope it helps to make clear what I want to archieve.

dflist <- mtcars %>%
  split(.$cyl)

lapply(dflist, function(x) dplyr::filter(x[["mpg"]] > 10))

Upvotes: 2

Views: 223

Answers (1)

akrun
akrun

Reputation: 887098

The filter works on a data.frame/tbl_df. Instead, we are extracting a vector (x[["mpg"]]) 

library(tidyverse)
filter(mtcars$mpg > 10)

Error in UseMethod("filter_") : no applicable method for 'filter_' applied to an object of class "logical"

and apply filter on it.

We need to apply filter on the data.frame itself

map(dflist, ~ .x %>% 
                 filter(mpg > 10))
#$`4`
#    mpg cyl  disp  hp drat    wt  qsec vs am gear carb
#1  22.8   4 108.0  93 3.85 2.320 18.61  1  1    4    1
#2  24.4   4 146.7  62 3.69 3.190 20.00  1  0    4    2
#3  22.8   4 140.8  95 3.92 3.150 22.90  1  0    4    2
#4  32.4   4  78.7  66 4.08 2.200 19.47  1  1    4    1
#5  30.4   4  75.7  52 4.93 1.615 18.52  1  1    4    2
#6  33.9   4  71.1  65 4.22 1.835 19.90  1  1    4    1
#7  21.5   4 120.1  97 3.70 2.465 20.01  1  0    3    1
#8  27.3   4  79.0  66 4.08 1.935 18.90  1  1    4    1
#9  26.0   4 120.3  91 4.43 2.140 16.70  0  1    5    2
#10 30.4   4  95.1 113 3.77 1.513 16.90  1  1    5    2
#11 21.4   4 121.0 109 4.11 2.780 18.60  1  1    4    2

#$`6`
#   mpg cyl  disp  hp drat    wt  qsec vs am gear carb
#1 21.0   6 160.0 110 3.90 2.620 16.46  0  1    4    4
#2 21.0   6 160.0 110 3.90 2.875 17.02  0  1    4    4
#3 21.4   6 258.0 110 3.08 3.215 19.44  1  0    3    1
#4 18.1   6 225.0 105 2.76 3.460 20.22  1  0    3    1
#5 19.2   6 167.6 123 3.92 3.440 18.30  1  0    4    4
#6 17.8   6 167.6 123 3.92 3.440 18.90  1  0    4    4
#7 19.7   6 145.0 175 3.62 2.770 15.50  0  1    5    6

#$`8`
#    mpg cyl  disp  hp drat    wt  qsec vs am gear carb
#1  18.7   8 360.0 175 3.15 3.440 17.02  0  0    3    2
#2  14.3   8 360.0 245 3.21 3.570 15.84  0  0    3    4
#3  16.4   8 275.8 180 3.07 4.070 17.40  0  0    3    3
#4  17.3   8 275.8 180 3.07 3.730 17.60  0  0    3    3
#5  15.2   8 275.8 180 3.07 3.780 18.00  0  0    3    3
#6  10.4   8 472.0 205 2.93 5.250 17.98  0  0    3    4
#7  10.4   8 460.0 215 3.00 5.424 17.82  0  0    3    4
#8  14.7   8 440.0 230 3.23 5.345 17.42  0  0    3    4
#9  15.5   8 318.0 150 2.76 3.520 16.87  0  0    3    2
#10 15.2   8 304.0 150 3.15 3.435 17.30  0  0    3    2
#11 13.3   8 350.0 245 3.73 3.840 15.41  0  0    3    4
#12 19.2   8 400.0 175 3.08 3.845 17.05  0  0    3    2
#13 15.8   8 351.0 264 4.22 3.170 14.50  0  1    5    4
#14 15.0   8 301.0 335 3.54 3.570 14.60  0  1    5    8

Or using lapply

lapply(dflist, function(x) x %>% 
                              filter(mpg > 10))

Upvotes: 1

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