split on factor, sapply, and lm [duplicate]

Answer 1

By the sounds of it, this might be what you're trying to do:

sapply(s, FUN= function(x)
  lm(x[ ,"dep"] ~ x[,"ind"])$coefficients[c(1, 2)])
#                      a          b          c
# (Intercept) 0.71379430 -0.6817331  0.5717372
# x[, "ind"]  0.07125591  1.1452096 -1.0303726

---

Other alternatives, if this is what you're looking for

I've seen it noted that in general, if you're splitting and then using s/lapply, you can usually just jump straight to by and skip the split step:

do.call(rbind, 
        by(data = df, INDICES=df$subj, FUN=function(x) 
          lm(x[, "dep"] ~ x[, "ind"])$coefficients[c(1, 2)]))
#   (Intercept)  x[, "ind"]
# a   0.7137943  0.07125591
# b  -0.6817331  1.14520962
# c   0.5717372 -1.03037257

Or, you can use one of the packages that lets you do such sorts of calculations more conveniently, like "data.table":

library(data.table)
DT <- data.table(df)
DT[, list(Int = lm(dep ~ ind)$coefficients[1],
          Slo = lm(dep ~ ind)$coefficients[2]), by = subj]
#    subj        Int         Slo
# 1:    a  0.7137943  0.07125591
# 2:    b -0.6817331  1.14520962
# 3:    c  0.5717372 -1.03037257

Answer 2

How about nlme::lmList?

library(nlme)

coef(lmList(dep~ind|subj,df))
##   (Intercept)         ind
## a   0.7137943  0.07125591
## b  -0.6817331  1.14520962
## c   0.5717372 -1.03037257

You can transpose this if you want.