Fitting mixed models in R (with lme4)

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Learning Objectives:
* Understand lmer syntax (fixed, random, cluster)
* Understand how to interpret fixed effect parameters
Here's the dataset I'm using: quantpsych.net/data/jedi.csv
Here's my video that shows you how to identify your cluster variable: • How to identify your c...
Here's a video about how to determine whether an effect is fixed or random: • How to decide whether ...
Link about EDA versus CDA: • Ethics in Statistics P...
My Multivariate playlist: • Multivariate Statistics
And here's a paper I wrote about my eight step approach to data analysis: psyarxiv.com/r8g7c/
Undergraduate curriculum playlist (GLM-based approach): ru-vid.com?list...
Graduate curriculum playlist (also GLM-based approach): ru-vid.com?list...
Exonerating EDA paper: psyarxiv.com/5vfq6/
Download JASP (and visual modeling module): www.jasp-stat.org

Опубликовано:

12 окт 2022

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Комментарии : 39

@QuantPsych Год назад

Yes, I know my head is in the way of the output. Sorry! But you should still get an idea of how to do these things in R.

@igorcastro6776 Год назад

When will you upload the next video? I'm desperately waiting for it!

@vinitalec 19 дней назад

Your videos are excellent!Thanks for helping me understand this subject.

@martinabautista 5 месяцев назад

You're funny. I feel glad to came across your content!! I'm using lme4 for my dissertation project

@msimister4261 11 месяцев назад

This was extremely helpful... Thank you so much for this!

@farmz0r Год назад

07:40 unfortunately your head is blocking the summary table you are talking about :d 5 referred to fixed effect intercept estimate 3.261 referred to random effects residual Variance 1.8 referred to random effects residual SD cba to do it for the next table atm

@chrislloyd5415 Год назад

Interested in your view about the following question. Your third model allows slope(darkness,anger) to depend on jedi_id. You could also just add an interaction term darkness*factor(jedi_id) right? Assuming this model is identifiable (and I think it is because anger is varying over time within jedi_id) what is the value of the random effects model which makes the arbitrary assumption that the jedi-specific slopes follow a normal distribution?

@EmmaCalikanzaros 5 месяцев назад

Thanks, I found your video super helpful. Could you explain what it means when the error "singular model" apprears?

@elena.s.v. 5 месяцев назад

Hello! Thank you for your videos, they help a lot. Would it be possible to get more information about the warnings one gets when fitting a random effect model, called "full" in your videos (e.g. singularity, did not converge, etc.) and how to solve them? I used the model comparison to verify whether I should fit a variable as a fixed effect only or as a fixed/random effect and some of my "full" models do not converge or "are singular". I also get warnings when trying to fit my final models (linear mixed model and generalized mixed models (poisson and negative binomial). Thank you for your help!

@mykiawiggins3318 6 месяцев назад

Not a fistbump...😳You punched my face!🤣😂 Thank goodness for your videos you're so frrreakin FUNNIEEEEE!

@ALI_B 9 месяцев назад

awesome video. I have a question : I have two clustering variables for a finance dataset where data is nested in banks and scores are time series reported quarterly. How to include the variable date in the script for the fixed model : fixed_y = lmer(y ~ 1 + x1 + x2 + x4 + x4 + (1 | Bank))

@QuantPsych 4 месяца назад

Good question. I think the proper notation is "...(1|Bank:Time)"

@zimmejoc Год назад

In the CSV file, the variable is named dojo_id not jedi_id. I always tell my students, "KNOW THY DATA" and that applies to me too. Bad zim for blindly typing what was in the video instead of verifying with the data first :)

@QuantPsych Год назад

Good catch!

@nikashomeil2369 2 месяца назад

Thank you so much for your wonderful video, I have a question, I have a model in which my fixed effect has 3 levels but when I ask for the summary one of the levels is not reported in the fixed effect, do you have any idea why is that?

@Lello991 Год назад

Hi prof Fife, I have a question for you: let's assume you want to add age_started as a predictor of darkness. Of course age_started doesn't vary within each level of the jedi_id cluster variable (i.e., each jedi has just a unique value of age_started). Could you add it with no problems? Is it possible to use age_started as fixed effect + jedi_id as random effect together? Or would you encounter some separation / convergence issues? I'm struggling to understand this point but I feel kind of lost. Thank you for your enlightening videos!

@nachete34 Год назад

As always, love ur videos, specially if they involve R. However, while it did not prevent me from following you, your face camera occluded the results window..just being picky :) Different topic...do u consider uploading some machine learning tutorial for dummies?

@EW-to9sr Год назад

Hello, thanks for uploading these tutorial videos. I'm a uni student trying to understand statistics in R and I found your channel is extremely helpful, thanks! Besides, I'd like to know is it reasonable to consider a factor as fixed and random at the same time? Looking forward to seeing you how explain the mixed model in following videos!

@QuantPsych Год назад

Yes. All random effects also have fixed effects. You cannot have a random effect without a fixed effect.

@jorgemmmmteixeira Год назад

In there a scenario where makes sense to have random slope and intercept for jedi_id? If so, how would you code it? thx

@QuantPsych Год назад

I'm not sure I understand your question...cluster variables don't have random slopes and intercepts. Variables do.

@taranaferdous2858 2 месяца назад

Hi! Thank you for this clear explanation. I followed the same for my data (data is in the same format that you have shown). My models worked fine up to fixed part. The moment I added the random part (1 + *** | ID), I got this error : number of observations (=100) < = number of random effect for term (1 + *** | ID). What am I missing here or doing wrong?

@IbrahimKwakuDuah 2 месяца назад

It is not 1+*, I guess the * would mean everything but you can't do everything

@trueperson22 Год назад

Thank you.. If you can explain the difference between the model with ~1 and the last one, I 'd really appreciate that..

@QuantPsych Год назад

~1 just means to fit an intercept. If it's omitted, R will fit an intercept anyway. The first model (baseline) has to have it because there are no predictors (i.e., fitting this will throw an error: lmer(y~ ( | id), data=d)). For the remaining models, it's redundant, but I put it there so you can easily track what I've added to the model.

@mind_palace 4 месяца назад

Repeated measures....to make sense of it, I'd say it could be that every measure per jedi_id, could be the therapist measuring their anger level for every session?

@QuantPsych 4 месяца назад

That works :)

@marcellberto2538 Год назад

Head's in the way bro! 😜 Still luvs ya videos though, as always thanks for sharing 😊

@ropflpfopfl2555 Год назад

Hey, i really like your video and your way of explaining things. Way clearer and simpler than other channels out here :D it is a great example on how mixed models work. However, i may have an understanding problem when it comes to the data format. At 3:40 you say that in their first year, when they are 5, they already killed someone. Does the dataset offers any time-specific variable? because the 5 stands for the point in time they started training, which should be always the same when looking at one jedi. (here jedi_id = jedi_1). Did I miss something? I'm only a poliscience student who stumbled upon that one :)

@QuantPsych 4 месяца назад

Ah, good point. I was getting really worried that five year olds were murdering people, but you're right. They might have waited until they were seven :)

@ceciliacocucci8288 Год назад

Dear Dustin I really enjoy your videos and love flexplot, but you always fit linear models. I'm a neonatologist, and almost 90% of my outcomes are binary o dichotomous. Is it possible to give usa video about non linear mixed models, aka logistic, ordinal etc.. ? I guess you'll use the nlme function but I'd really love to have your explanations. Thanks!!!

@QuantPsych Год назад

I'm pretty sure I made a generalized mixed model video. I think it was poisson mixed models, but it might have been logistic. Just take my logistic regression videos, combine those with my mixed models videos, and you'll get it.

@ladynoluck Год назад

Definitely not watching this as a SAS to R transplant for my dissertation 😂

@hanswurst4728 Год назад

Cool, but if we could actually see the output while you're interpreting it and not your face, that would be tremendously helpful. Informative nonetheless 👍.

@dle3528 9 месяцев назад

Your head is in front of the output 😕

@QuantPsych 4 месяца назад

I can't help having a fat head :)

@chrislloyd5415 Год назад

Why is it a 1? You reallj don't know? C'mon man! (Just call me Joe Biden). It obviously refers to a column of 1's in the design matrix.

@diptarshis 3 месяца назад

Could you please stop with the clowning and get on with the explanations. Your attempt at deadpan humor sucks. You're way better at teaching, do that please !

@QuantPsych 3 месяца назад

No, it's so deeply ingrained in my personality. I do me, you do you. And it seems you're outvoted. Everyone else seems to like it :)