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In R, when I select only one column from a data frame/matrix, the result will become a vector and lost the column names, how can I keep the column names? For example, if I run the following code,
x <- matrix(1,3,3)
colnames(x) <- c("test1","test2","test3")
x[,1]
I will get
[1] 1 1 1
Actually, I want to get
test1
[1,] 1
[2,] 1
[3,] 1
The following code give me exactly what I want, however, is there any easier way to do this?
x <- matrix(1,3,3)
colnames(x) <- c("test1","test2","test3")
y <- as.matrix(x[,1])
colnames(y) <- colnames(x)[1]
y
715
To select a column in R you can use brackets e.g., YourDataFrame['Column'] will take the column named “Column”. Furthermore, we can also use dplyr and the select() function to get columns by name or index. For instance, select(YourDataFrame, c('A', 'B') will take the columns named “A” and “B” from the dataframe.
We use colnames() function for renaming the matrix column in R. It is quite simple to use the colnames() function. If you want to know more about colnames() function, then you can get help about it in R Studio using the command help(colnames) or ? colnames().
To access a specific column in a dataframe by name, you use the $ operator in the form df$name where df is the name of the dataframe, and name is the name of the column you are interested in. This operation will then return the column you want as a vector.
Use the drop argument:
> x <- matrix(1,3,3)
> colnames(x) <- c("test1","test2","test3")
> x[,1, drop = FALSE]
test1
[1,] 1
[2,] 1
[3,] 1
Another possibility is to use subset:
> subset(x, select = 1)
test1
[1,] 1
[2,] 1
[3,] 1
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