Indexing and looping over lists in R, a tutorial (CC174)

Lists are an important, but underappreciated type of data in R. In this Code Club, Pat gives a tutorial on indexing or accessing values from a list and then shows how we can iterate over the values of a list using the lapply function. Along the way we'll see how we can unlist lists and convert them into matrices as well as generate the transpose of a matrix with the t function. This is part of a series of videos demonstrating how to functions from base R to make these data compatible with tools from the tidyverse
You can find my blog post for this episode at www.riffomonas.org/code_club/....
The data were generated in our Kozich et al. 2013 paper (doi.org/10.1128/AEM.01043-13) using samples from the Schloss et al. 2012 paper (doi.org/10.4161/gmic.21008).
#list #lapply #R #Rstats #baseR
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If you're interested in taking an upcoming 3 day R workshop be sure to check out our schedule at riffomonas.org/workshops/
You can also find complete tutorials for learning R with the tidyverse using...
Microbial ecology data: www.riffomonas.org/minimalR/
General data: www.riffomonas.org/generalR/
0:00 Using lists and lapply to replace a for loop
1:31 Parsing a file on line breaks with scan
3:53 Splitting text data with strsplit
5:57 How to access values from a list
8:35 Creating a function to make list elements the same length
11:43 Iterating a function over values in a list with lapply
13:51 Merging elements of a list with unlist and do.call
16:14 Converting lower triangular matrix to a full matrix

[@CBG91]

Your explanation that dataframes are actually lists of vectors blew my mind. None of my instructors have ever made that explicit!

[@Riffomonas]

Wonderful! Thanks for watching 😊

[@dimamedvedev4124]

great exapmles and smart explanation

Learning a lot from your videos. Happy holidays!

[@Riffomonas]

Hi Victor - wonderful! Thanks for watching

[@luisandresmorenocueva3399]

Merry xmas. Thx for the videos of this year

[@Riffomonas]

Thanks Luis! Have a great Christmas 😊

[@marcossahade9369]

very interesting lessons .. congrats from Argentina

[@Riffomonas]

Hi Marcos - Thanks for watching!

[@tlange5091]

Thank you so much for your videos!

[@Riffomonas]

My pleasure! Thanks for tuning in 🤓

[@oluwafemioyedele]

Nice tutorial!!!

[@Riffomonas]

Thanks- glad it was useful!

[@roymccormick5328]

cool thx

[@Riffomonas]

Thanks for watching!

[@domenicoscarpino3715]

Hi, thanks a lot for the great content.
I don't seem to be able to explain why they included [,1] in the code below. I was checking a solved exercise and found this code, so I thought I could maybe ask here about the theoretical explanation behind that specific part. I would have thought that Data[,i] was enough to make it work. Thanks in advance.
for(i in c(2,6:11)){
a=(abs(scale(Data[,i])[,1])

[@Riffomonas]

Thanks for the question. Unfortunately, I am unable to answer questions like this in comments. I'd encourage you to ask on StackOverflow or on the RStudio forum