CODEWITHSUNDEEP
r
Klemz
Klemz

Reputation: 143

Filter table by column in R

I would like to filter table if I have column name written in variable. I tried bellow code but it did not work. dat is a data frame, name of column is Name, and I would like to filter by "John".

colname <- "Name"
dat[dat$colname %in% "John",]

I saw that it works fine if I do not use variable for column name. (Bellow code works fine)

dat[dat$"Name" %in% "John",]

Upvotes: 1

Views: 515

Answers (3)

akrun
akrun

Reputation: 887088

With data.table, we can use eval with as.symbol

library(data.table)
setDT(dat)[eval(as.symbol(colname)) == "John"]
#  Name         X1         X2
#1: John  0.8646536  1.2688507
#2: John -1.7201559 -0.3125515

Upvotes: 0

Ronak Shah
Ronak Shah

Reputation: 388982

An approach with dplyr using non-standard evaluation. Using @jay.sf's data

library(dplyr)
dat %>% filter(!!sym(colname) == "John")

#  Name        X1        X2
#1 John  0.864654  1.268851
#2 John -1.720156 -0.312552

In data.table, we can use get

library(data.table)
setDT(dat)[get(colname) == "John"]

Since we have only one value to compare we can use == here instead of %in%.

Upvotes: 0

jay.sf
jay.sf

Reputation: 72758

You may use the bracket function [.

colname <- "Name"

dat[dat[[colname]] %in% "John", ]
dat[dat[, colname] %in% "John", ]  # or
#   Name         X1         X2
# 8 John  0.8646536  1.2688507
# 9 John -1.7201559 -0.3125515

Data

dat <- structure(list(Name = structure(c(3L, 3L, 2L, 4L, 4L, 2L, 3L, 
1L, 1L, 2L), .Label = c("John", "Linda", "Mary", "Olaf"), class = "factor"), 
    X1 = c(0.758396178001042, -1.3061852590117, -0.802519568703793, 
    -1.79224083446114, -0.0420324540227439, 2.15004261784474, 
    -1.77023083820321, 0.864653594565389, -1.72015589816109, 
    0.134125668141181), X2 = c(-0.0758265646523722, 0.85830054437592, 
    0.34490034810227, -0.582452690107777, 0.786170375925402, 
    -0.692099286413293, -1.18304353631275, 1.26885070606311, 
    -0.31255154601115, 0.0305712590978896)), class = "data.frame", row.names = c(NA, 
-10L))

Upvotes: 2

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