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Drop Columns R Data frame
Let's say I have a dataframe with column c1, c2, c3.
I want to list just c1 and c2. How do I do that?
I've tried:
head(data[column!="c3"]) head(data)[,2] head(data[!"c3"]) 
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To pick out single or multiple columns use the select() function. The select() function expects a dataframe as it's first input ('argument', in R language), followed by the names of the columns you want to extract with a comma between each name.
The most easiest way to drop columns is by using subset() function. In the code below, we are telling R to drop variables x and z. The '-' sign indicates dropping variables. Make sure the variable names would NOT be specified in quotes when using subset() function.
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.
If you are looking for negative indexing by name (in addition to tcash21's numeric indexing), here's a few ways I know, some riskier than others:
mtcars[, -which(names(mtcars) == "carb")] #only works on a single column mtcars[, names(mtcars) != "carb"] #only works on a single column mtcars[, !names(mtcars) %in% c("carb", "mpg")] mtcars[, -match(c("carb", "mpg"), names(mtcars))] mtcars2 <- mtcars; mtcars2$hp <- NULL #lost column (risky) library(gdata) remove.vars(mtcars2, names=c("mpg", "carb"), info=TRUE) Generally I use:
mtcars[, !names(mtcars) %in% c("carb", "mpg")] because I feel it's safe and efficient.
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You can index and use a negative sign to drop the 3rd column:
data[,-3] Or you can list only the first 2 columns:
data[,c("c1", "c2")] data[,1:2] Don't forget the comma and referencing data frames works like this: data[row,column]
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