r - Extract items in nested lists -

i have problem: work data frame development time (dependent variable) of 5 species according temperature (independent variable) "by" function calculated lm's of 5 species

by(dados, dados$especie, function(dados) lm(dados$tempo ~ dados$temp, data = dados) 

and result got lists nested in other lists yo can see here

list of 5  $ c.albiceps   :list of 12   ..$ coefficients : named num [1:2] 262.78 -1.76   .. ..- attr(*, "names")= chr [1:2] "(intercept)" "dados$temp"   ..$ residuals    : named num [1:41] -4.157 -2.394 -0.631 1.131 2.894 ...   .. ..- attr(*, "names")= chr [1:41] "1" "2" "3" "4" ...   ..$ effects      : named num [1:41] -1344.031 -133.548 0.235 1.977 3.72 ...   .. ..- attr(*, "names")= chr [1:41] "(intercept)" "dados$temp" "" "" ...   ..$ rank         : int 2 

it's list of 5 elements (one each specie), , each specie list of 12 elements (from lm function). so, 5 lists of 12, within list of 5.

now, question: want extract values coefficients , sum them up. got list$speciesname$coefficients[2] , want extract each value (the second item of $coefficients, each specie), , want save in vector (in order calculate indices it).

any helpful hints on that?

you can loop on models apply function , extract coefficients coef.

## example mods <- by(mtcars, mtcars$cyl, function(x) lm(mpg ~ disp, data=x))  ## sum second coefficients sum(sapply(mods, function(x) coef(x)[[2]]))