How to Extract Unique Elements from a Data.Frame in R

Extracting unique values from data frame using R

This is well suited for union:

data.frame(V1_V2=union(df$v1, df$v2))

#  V1_V2
#1     1
#2     2
#3     3
#4     a
#5     b
#6     4

How to extract unique elements from a data.frame in R?

A 'data.frame' can be considered as a 'list' with columns as 'list' elements having the same length. By using unlist, we can convert it to vector and then get the unique values and convert to 'character' class with as.character.

as.character(unique(unlist(df)))

How to extract unique values from a data frame column?

There are some typos in object names datframe and dataframe as well as curly brackets are misplaced:

val_uniques <- function(colname, dataframe) {
  if (colname %in% colnames(dataframe)) {
    print(unique(dataframe[, colname] , incomparables = FALSE))
  } else {
    print("cette colonne n'existe pas")
  }
}

df <- data.frame(a = c(1, 1, 3, 4), b = 1:4)

val_uniques("a", df)
# [1] 1 3 4

How to extract unique values from a data frame in r

Here is a base R approach:

There are two parts:

1. We create a list of positions that occur at least twice using duplicated
2. We look for positions that are not in the list of duplicated positions

Then we subset test on condition 2.

test[!test$position %in% test$position[duplicated(test$position)],]
#    position genomic_regions
#3 chr1_13538      intergenic

How to extract unique rows from a data frame with an index column?

You could use duplicated().

> df1[-which(duplicated(df1[,-1])), ]
  Index  a  b  c
1     1 12 12 14
3     3 11 12 13

Data

df1 <- structure(list(Index = 1:3, a = c(12L, 12L, 11L), b = c(12L, 
                                                               12L, 12L), c = c(14L, 14L, 13L)), class = "data.frame", row.names = c(NA, 
                                                                                                                                     -3L))

Unique values of a dataframe column to list in R

In base R, you can get unique values from site_name and make it a list.

as.list(unique(site_df$site_name))

For example, with default mtcars this will result into :

as.list(unique(mtcars$cyl))
#[[1]]
#[1] 6

#[[2]]
#[1] 4

#[[3]]
#[1] 8

get unique values of single column in list of data frames in R

We can unlist the data.frames and get the unique elements

unique(unlist(dd$data))
#[1] 1 2 3 4

If we need to extract only 'a' column

unique(unlist(lapply(dd$data, `[[`, "a")))
#[1] 1 2 3 4

---

Or with map/pluck

library(dplyr)
library(purrr)
map(dd$data,  pluck, "a") %>%
    flatten_dbl %>%
    unique
#[1] 1 2 3 4

R dataframe - how to extract unique values

No need to use summarise here, you can do this (using head to get the first row)

 ddply(sampleData, .(SUBJ, BLK, TR), function(x) head(x,1))
  SUBJ BLK TR    BEG    END
1 1234   1  1 111021 111021
2 1234   2  2 132050 133113
3 5678   1  1  82503  82502
4 5678   2  2 274870 288224

Or more general to get the nth row.n you can do :

ddply(sampleData, .(SUBJ, BLK, TR), function(x) x[min(row.n,nrow(x),])

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