comment on the code #create a list $...$

N $<-100$

X $<-$ vector$("$list$",$ N$)$

for $($i in $1$:N$)\{$

name $<-$ paste$0("$n$",$ i$)$

vect $<-$ rnorm$(5,$ mean $=20,$ sd $=10)$

X$[[$i$]]<-$ list$($name $=$ name, vect $=$ vect$)$

$\}$

#show the structure of X

str$($X$)$

# Compute the sum of the values of vect in each slot

sums$\_$vect $<-$ sapply$($X$,$ function$($x$)$ sum$($x$vect$))$

print$($sums$\_$vect$)$

# Create a matrix M of size $100$x$5$

M $<-$ do$.$call$($rbind$,$ lapply$($X$,$ function$($x$)$ x$vect$))$

print$($M$)$

# Compute the sums by columns of M

column$\_$sums $<-$ numeric$($ncol$($M$))$

for $($j in $1$:ncol$($M$))\{$

column$\_$sums$[$j$]<-$ sum$($M$[,$ j$])$

$\}$

print$($column$\_$sums$)$