Get row names based on column values, R, multiple conditions

Question

Using the sample data set mtcars

head(mtcars)
                   mpg cyl disp  hp drat    wt  qsec vs am gear carb
Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1

I want to get the rownames into a vection in all cases where the cyl==4|cyl==6

I found the code

rowname_vec<-which(mtcars[mtcars$cyl==4,])

But I do not know how to make this work with multiple conditions. (getting the row names for 4 a 6 cyl cars)

S-SHAAF · Answer 1 · 2023-03-02T17:16:45.167

Using | operator you could filter for multiple cyl values:

rowname_vec <- rownames(mtcars[mtcars$cyl==4 | mtcars$cyl==6,])

rowname_vec

 [1] "Mazda RX4"      "Mazda RX4 Wag"  "Datsun 710"     "Hornet 4 Drive" "Valiant"        "Merc 240D"      "Merc 230"       "Merc 280"       "Merc 280C"     
[10] "Fiat 128"       "Honda Civic"    "Toyota Corolla" "Toyota Corona"  "Fiat X1-9"      "Porsche 914-2"  "Lotus Europa"   "Ferrari Dino"   "Volvo 142E"

Or using filter() from tidyverse family:

library(tidyverse)
rowname_vec <- rownames(filter(mtcars, cyl == 4  | cyl == 6))
rowname_vec

     [1] "Mazda RX4"      "Mazda RX4 Wag"  "Datsun 710"     "Hornet 4 Drive" "Valiant"        "Merc 240D"      "Merc 230"       "Merc 280"       "Merc 280C"     
    [10] "Fiat 128"       "Honda Civic"    "Toyota Corolla" "Toyota Corona"  "Fiat X1-9"      "Porsche 914-2"  "Lotus Europa"   "Ferrari Dino"   "Volvo 142E"

score 4 · Accepted Answer · answered Mar 02 '23 at 17:07

4

Using %in%

row.names(mtcars)[with(mtcars, cyl %in% c(4, 6))]

answered Mar 02 '23 at 17:07

akrun

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Accepted this answer vs the one below because the result gives me a vector of rownames that I can then use to subset the data the same way, regardless of if the number of rows of the data frame changes (ie, updates to the raw data) – M3Lba Mar 02 '23 at 19:16
both row.names() and rownames() can be used to achieve the same result of extracting the row names of a data frame as a vector and using that vector to subset the data frame. The choice between the two functions is just comes down to personal preference. – S-SHAAF Mar 02 '23 at 19:52

score 0 · Answer 3 · answered Mar 02 '23 at 20:37

A base option using subset + row.names

> row.names(subset(mtcars, abs(cyl - 5) == 1))
 [1] "Mazda RX4"      "Mazda RX4 Wag"  "Datsun 710"     "Hornet 4 Drive"
 [5] "Valiant"        "Merc 240D"      "Merc 230"       "Merc 280"
 [9] "Merc 280C"      "Fiat 128"       "Honda Civic"    "Toyota Corolla"
[13] "Toyota Corona"  "Fiat X1-9"      "Porsche 914-2"  "Lotus Europa"
[17] "Ferrari Dino"   "Volvo 142E"

Get row names based on column values, R, multiple conditions

3 Answers3