Creating new variables by writing a function

[annajames.t]

Hi, I'm doing a Biostatistics course and am trying to figure out how to make a new variable from a data set I already uploaded.
I want to label the variable "effect", and have it show the difference between the 'grass' samples and the 'spruce' samples of each 'box' as shown in the console.
Seems like there's probably a simple solution but can't find anything.

[FJCC]

One solution is

spruce$effect <- spruce$Spruce - spruce$Grass

[williaml]

Hi, next time please provide a reproducible example instead of a screenshot.

Anyway, here is some code that should work. You could also calculate the absolute difference with the abs() function.

library(tidyverse)

# tidyverse way
spruce <- spruce %>% 
  mutate(diff = Grass - Spruce) 


# base R way
spruce$diff <- spruce$Grass - spruce$Spruce

FAQ: How to do a minimal reproducible example ( reprex ) for beginners

A minimal reproducible example consists of the following items: A minimal dataset, necessary to reproduce the issue The minimal runnable code necessary to reproduce the issue, which can be run on the given dataset, and including the necessary information on the used packages. Let's quickly go over each one of these with examples: Minimal Dataset (Sample Data) You need to provide a data frame that is small enough to be (reasonably) pasted on a post, but big enough to reproduce your issue. Let's say, as an example, that you are working with the iris data frame head(iris) #> Sepal.Length Sepal.Width Petal.Length Petal.Width Species #> 1 5.1 3.5 1.4 0.…

[annajames.t]

Thank you this helped a lot.

[annajames.t]

Hi sorry I'm new here on the forum, will definitely do that next time!