Extract Formula From lm with Coefficients (R)

Question

I have an lm object and want to get the formula extracted with coefficients. I know how to extract the formula without coefficients, and how to get the coefficients without the formula, but not how to get eg. y ~ 10 + 1.25b as opposed to y~b or a table of what intercept, b etc. equal

This is the code I'm working with currently:

a = c(1, 2, 5)
b = c(12, 15, 20)

model = lm(a~b)
summary(model)
formula = formula(model)
formula
coefficients(model)

What I'd like to get from the above is y ~ -5.326 + .51b

Thanks

Edit: In my actual code I'm working with over 63 predictors and 18 different models, so I'd like something that can scale up without too much work.

Answer 1

as.formula(
  paste0("y ~ ", round(coefficients(model)[1],2), " + ", 
    paste(sprintf("%.2f * %s", 
                  coefficients(model)[-1],  
                  names(coefficients(model)[-1])), 
          collapse=" + ")
  )
)
# y ~ -5.33 + 0.51 * b