Multiple linear regression with interaction in R

Need to include interaction with a categorical variable in your linear model in R? Start here.
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[Sam_a]

THANK YOU. This is the clearest explanation I've found. It's not that complicated but for some reason it's so hard to find a clear explanation.

[meseretmuche]

Impressive video, thank you so much.
Q. how to add confidence interval, statistics like p-value and correlation in multiple regression? Thank for your time and collaboration.

[max]

Great video we hope more about logistic regression

[haraldurkarlsson]

Here is my question. How do we know which is which in terms of the dependent and independent variables? In other words which is true? Flipper length controls body mass or body mass controls flipper length?

[brazilfootball]

Would you recommend mean-centering "flipper_length_mm" first or is it not necessary? If so, can you recommend a resource for how to do it in R and how to interpret the results?

[freshhbresh]

If you had say 5 dependant variables and a 2 level factor variables, say species, do you need to multiply every dependent by species in the lm function?

[neiltalbert]

Helped with a conference paper. Thanks

[anitasosa]

Hey, thanks a lot for this video!! Made my study a bit clearer. However, I'm struggling with my data bundle, and I'd like to ask for your help.

In my case, the equivalent to bodymass would be transcripts per million (TPM: the amount of normalized transcripts of a specific gene). Flipper length would be a categorical variable, 'Exponential' and 'Stationary', and the Species would be the Treatment to which the cells have been submitted (Solid or Liquid growth). I'm struggling with the concept of the slope because my x variable is not numerical. Would you have some input about this? Thank you very much!

[samanthajooodemannn]

Can you do multiple interactions with this method? Like if you wanted to split up the data for flipper length for male Chinstrap, female Chinstrap, male Gentoo, and female Gentoo so you get 4 lines to compare to each other.

[brazilfootball]

Great video, thank you! I'm confused though about the equation for the theory vs. in R. Why is the equation y = b0 + b1x1 +b2x2 +b3x1*x2, but we write it in R as glm(x1 ~ x2*x3...) instead of glm(x1 ~ x2 + x3 + x2*x3...)? As in: body_mass_g ~ flipper_length_mm + species + flipper_length_mm * species? Hopefully that's clear, haha.

[ConorBlunt]

Thanks very much for the great instructional video. Much appreciated! Can you help me with a minor detail please?
I have 4 levels of a categorical variable('biostimulant') and my linear model summary output lists this variable by name then a number eg, Biostimulant1, Biostimulant2 etc.
How does one identify what the variable name is, that R has assigned 1, 2, 3, 4?
Thanks in advance!

[Jaymastia]

You look and sound like little finger from game of thrones