If I understand your code correctly, you're predicting Runs (R) from Walks (BB) and Home runs (HR) per game. Which this would do:
library(tidyverse)
library(Lahman)
lm_data <- Teams %>%
filter(yearID %in% 1961:2018) %>%
mutate(BB = BB/G, HR = HR/G, R = R/G) %>%
group_by(yearID) %>%
lm(R ~ BB + HR, data = .)
summary(lm_data)
With your filter() function, you can get rid of it or filter Walks (BB) by a number. For example filter(BB > 3.0)