How Do Add a Column in a Data Frame in R

Adding a column to a dataframe in R

That is a pretty standard use case for apply():

R> vec <- 1:10
R> DF <- data.frame(start=c(1,3,5,7), end=c(2,6,7,9))
R> DF$newcol <- apply(DF,1,function(row) mean(vec[ row[1] : row[2] ] ))
R> DF
  start end newcol
1     1   2    1.5
2     3   6    4.5
3     5   7    6.0
4     7   9    8.0
R> 

You can also use plyr if you prefer but here is no real need to go beyond functions from base R.

How to add a new column in dataframe based on a single character in dataframe names?

Considering name restriction in R, I remove brackets from dataframe name, so I think the reproducible example should be something like this :

df_list <- list()
Height <- c(175,180,179)
Weight <- c(75,85,79)
Person <- c('Alex','Gerard','Clyde')
df_list$'1.3.A' <- data.frame(Person,Height,Weight)
Person <- c('Missy','Britany','Sussie')
df_list$'2.2.A' <- data.frame(Person,Height,Weight)
Person <- c('Luke','Alex','Haley')
df_list$'1.1.B' <- data.frame(Person,Height,Weight)

$`1.3.A`
  Person Height Weight
1   Alex    175     75
2 Gerard    180     85
3  Clyde    179     79

$`2.2.A`
   Person Height Weight
1   Missy    175     75
2 Britany    180     85
3  Sussie    179     79

$`1.1.B`
  Person Height Weight
1   Luke    175     75
2   Alex    180     85
3  Haley    179     79

Without using any libraries, similar to Anoushiravan R, I use strsplit and Map to extract Trial, Day and Group value from dataframe name :

ColAdd <- \(DF,Names){
  DF[,c('Trial','Day','Group')] <- 
    (Names |> strsplit(split = '.', fixed = T))[[1]] |> 
    rep(nrow(DF)) |> 
    matrix(ncol=3,byrow = T)
  return(DF)
}

df_list <- Map(ColAdd,df_list,names(df_list))

$`1.3.A`
  Person Height Weight Trial Day Group
1   Alex    175     75     1   3     A
2 Gerard    180     85     1   3     A
3  Clyde    179     79     1   3     A

$`2.2.A`
   Person Height Weight Trial Day Group
1   Missy    175     75     2   2     A
2 Britany    180     85     2   2     A
3  Sussie    179     79     2   2     A

$`1.1.B`
  Person Height Weight Trial Day Group
1   Luke    175     75     1   1     B
2   Alex    180     85     1   1     B
3  Haley    179     79     1   1     B

How do I add a column to a data frame consisting of minimum values from other columns?

You can use apply() function to do this. See below.

df$C <- apply(df, 1, min)

The second argument allows you to choose the dimension in which you want min to be applied, in this case 1, applies min to all columns in each row separately.

You can choose specific columns from the dataframe, as follows:

df$newCol <- apply(df[c('A','B')], 1, min)

How do add a column in a data frame in R

You can use a map. (UPDATED to use stringsAsFactors = FALSE)

df <- data.frame( Name = c('A', 'C', 'D', 'E', 'H', 'Z', 'M'), 
                  Count = c(100,10,40,30,3,20,50), stringsAsFactors = FALSE)
Categories <- list(Cat1 = c('A','D'), 
                   Cat2 = c('C','Z'), 
                   Cat3 = c('E','H'), 
                   Cat10 = 'M')
nams <- names( Categories )
nums <- sapply(Categories, length)
CatMap <- unlist( Map( rep, nams, nums ) )
names(CatMap) <- unlist( Categories )

df <- transform( df, Category = CatMap[ Name ])

R - Add a column of data to an existing column in a dataframe

You will need to make sure that the column names are same when appending data.

In your case:

df2 <- data.frame(x2, y2)   #creating a dataframe
names(df2) <- names(df)     #changing the column header names as this is a requirement for append

df <- rbind(df, df2)    #appending

R: How do I add a column to a dataframe based on paired values in another dataframe with different length?

Using left_join from dplyr package:

library(dplyr)

data <- left_join(df1,df2, by="id")

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