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I think I am missing a fundamental concept about R's data frames.
head(mtcars)
mpg cyl disp hp drat wt qsec vs am gear carb
Mazda RX4 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
Mazda RX4 Wag 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
Datsun 710 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
Hornet 4 Drive 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
Hornet Sportabout 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
Valiant 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1
The names of the cars here. Is this a column? I don't think so, because I am not able to access them via mtcars[,1]. And there is no column name/header for it.
How could I create a data frame like that? How could I use that special column e.g. to describe the data in a plot for example?
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What is this? We can see that the dataset has 32 rows and 11 columns.
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.
To rename a column in R you can use the rename() function from dplyr. For example, if you want to rename the column “A” to “B”, again, you can run the following code: rename(dataframe, B = A) .
"Answer: 200000 per mile is the average mileage of a car in the mtcars given dataset.
A shorter one liner argument with data.tablePackage will make the rowname a column.
library(data.table)
setDT(mtcars, keep.rownames = TRUE[])
head(mtcars)
rn mpg cyl disp hp drat wt qsec vs am gear carb
Mazda RX4 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
Mazda RX4 Wag 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
Datsun 710 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
Hornet 4 Drive 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
Hornet Sportabout 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
Valiant 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1
This works too using tibble.
library(tibble)
mtcars %>%
rownames_to_column(var="carnames")
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