如何获得具有自己价值的矩阵

Question

我希望获得1000行和20列具有prob值。

set.seed(12345678)
N<-1000 #row number
kitem<-20 # col number
result<- matrix(0,N,kitem)
for(i in 1:N){
for(j in 1:kitem){
theta1<-rnorm(20,0,1)
theta2<-rnorm(20,-0.5,1)
a1<-rnorm(20,1,1)
a2<-rnorm(20,1,1)
b=1
d<- -b*sqrt(a1^2+a2^2)
cc=0.5 
prob<- cc+(1-cc)/(1+exp(-((theta1*a1)+(theta2*a2)+d)))
}
}
result[i,j] <-prob