I'm an R veteran who usually hates working with nested lists because of how tricky they seem get... but I am not sure I can avoid them here. In this case, I can make the output that I want, but I'm clueless about how to intelligently take apart the list once it's made.
I'm trying to make n linear models from a dataset for each level of a class. After running all of the models, I want a simple table that houses the slopes, intercepts, and classes for each level. The example below is what I'm after:
# Dummy data
d <- data.frame(x=rnorm(50, 10, 1),
y=rnorm(50, 0, 2),
class=c(rep('A',10),rep('B',10),rep('C',10),rep('D',10),rep('E',10)))
# Split the data by grouping variable
d.s <- split(d, d$class)
# Create a linear model from y~x in each class
coeffs <- function(df) {
m <- lm(y~x, data = df)$coefficients
}
m.s <- lapply(d.s, coeffs)
# How do I neatly get a data frame that looks like below out of m.s??
wanted <- data.frame(class=as.character(), slope=as.numeric(), intercept=as.numeric())
Please excuse my aversion and inexperience with nested lists! I can get what I want after many lines of unlisting and picking apart the rownames, but there's got to be a better way. I'm trying to change...
You could use sapply in the first place,
> t(sapply(d.s, coeffs))
(Intercept) x
A 9.4390072 -0.8430022
B -5.2018384 0.4988027
C -7.9531678 0.8298487
D -0.9505984 0.1192621
E -1.8155237 0.1522270
> data.frame(sort(unique(d$class)), t(sapply(d.s, coeffs))) |>
+ setNames(c('class', 'intercept', 'slope'))
class intercept slope
A A 9.4390072 -0.8430022
B B -5.2018384 0.4988027
C C -7.9531678 0.8298487
D D -0.9505984 0.1192621
E E -1.8155237 0.1522270
Or if you depend on lapply, rbind result.
> data.frame(names(m.s), do.call('rbind', m.s)) |>
+ setNames(c('class', 'intercept', 'slope'))
class intercept slope
A A 9.4390072 -0.8430022
B B -5.2018384 0.4988027
C C -7.9531678 0.8298487
D D -0.9505984 0.1192621
E E -1.8155237 0.1522270
If you really want slope before intercept, do
> data.frame(class=names(m.s), do.call('rbind', m.s)[, 2:1]) |>
+ setNames(c('class', 'slope', 'intercept'))
class slope intercept
A A -0.8430022 9.4390072
B B 0.4988027 -5.2018384
C C 0.8298487 -7.9531678
D D 0.1192621 -0.9505984
E E 0.1522270 -1.8155237