Error in Linear Model

[mchien20]

library(mosaic) library(readr) DirtBikes <- read_csv("http://nhorton.people.amherst.edu/is5/data/Dirt_bikes_2014.csv") DirtBikes <- DirtBikes %>% filter(Cooling != "NA") %>% mutate(Cooling = ifelse(Cooling == "Air-Cooled", "Air-Cooled", "LiquidCooled")) gf_point(MSRP ~ (Displacement)^(1/3), color = ~ Cooling, data = DirtBikes) %>% gf_lm() bikeslm <- lm(MSRP ~ Displacement^(1/3) + Cooling, data = DirtBikes)

The last line of code gives me an error: Error in terms.formula(formula, data = data) : invalid power in formula I understand that it's because of Displacement^(1/3), but I'm not sure how to get around it. (Chapter 9, page 291)

[nicholasjhorton]

Try enclosing that term with the I() function. See ?I (Capital i) for details and examples.

All the best,

Nick

On Jul 3, 2018, at 11:38 AM, Margaret Chien notifications@github.com wrote:

library(mosaic) library(readr) DirtBikes <- read_csv("http://nhorton.people.amherst.edu/is5/data/Dirt_bikes_2014.csv") DirtBikes <- DirtBikes %>% filter(Cooling != "NA") %>% mutate(Cooling = ifelse(Cooling == "Air-Cooled", "Air-Cooled", "LiquidCooled")) gf_point(MSRP ~ (Displacement)^(1/3), color = ~ Cooling, data = DirtBikes) %>% gf_lm() bikeslm <- lm(MSRP ~ Displacement^(1/3) + Cooling, data = DirtBikes)

The last line of code gives me an error: Error in terms.formula(formula, data = data) : invalid power in formula I understand that it's because of Displacement^(1/3), but I'm not sure how to get around it.

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[nicholasjhorton]

I’m worried about the filter() command. Are these really coded as strings “NA”? I hope not. Using !is.na() would be far preferable if they are coded as NA.

All the best,

Nick

On Jul 3, 2018, at 11:38 AM, Margaret Chien notifications@github.com wrote:

library(mosaic) library(readr) DirtBikes <- read_csv("http://nhorton.people.amherst.edu/is5/data/Dirt_bikes_2014.csv") DirtBikes <- DirtBikes %>% filter(Cooling != "NA") %>% mutate(Cooling = ifelse(Cooling == "Air-Cooled", "Air-Cooled", "LiquidCooled")) gf_point(MSRP ~ (Displacement)^(1/3), color = ~ Cooling, data = DirtBikes) %>% gf_lm() bikeslm <- lm(MSRP ~ Displacement^(1/3) + Cooling, data = DirtBikes)

The last line of code gives me an error: Error in terms.formula(formula, data = data) : invalid power in formula I understand that it's because of Displacement^(1/3), but I'm not sure how to get around it.

— You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or mute the thread.

[nicholasjhorton]

Another option would be to generate the transformed variable in the mutate call. That might be my preference as the name would automatically show up in the plot.

All the best,

Nick

On Jul 3, 2018, at 11:38 AM, Margaret Chien notifications@github.com wrote:

library(mosaic) library(readr) DirtBikes <- read_csv("http://nhorton.people.amherst.edu/is5/data/Dirt_bikes_2014.csv") DirtBikes <- DirtBikes %>% filter(Cooling != "NA") %>% mutate(Cooling = ifelse(Cooling == "Air-Cooled", "Air-Cooled", "LiquidCooled")) gf_point(MSRP ~ (Displacement)^(1/3), color = ~ Cooling, data = DirtBikes) %>% gf_lm() bikeslm <- lm(MSRP ~ Displacement^(1/3) + Cooling, data = DirtBikes)

The last line of code gives me an error: Error in terms.formula(formula, data = data) : invalid power in formula I understand that it's because of Displacement^(1/3), but I'm not sure how to get around it.

— You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or mute the thread.