如何使用dmvnorm功能和mapply一起

Question

set.seed(1) 
### i would like to do this 
dmvnorm(c(.5,.5), mean= c(2,15), matrix(c(3, 0, 0, 9), 2)) 
dmvnorm(c(.6,.6), mean= c(5,18), matrix(c(6, 0, 0, 15), 2)) 

##### BUT using mapply instead... how can that be done? 
u1 = c(2,15) 
sigma1 = matrix(c(3, 0, 0, 9), 2) 
u2 = c(5, 18) 
sigma2 = matrix(c(6, 0, 0, 15), 2) 
parameters = list(mu = list(u1, u2), sigma = list(sigma1, sigma2)) 
mapply(c(c(.5,.5),c(.6,.6)), dmvnorm, 
     mean = c(parameters$mu[[1]], parameters$mu[[2]]) , 
     sigma= c(parameters$sigma[[1]],parameters$sigma[[2]] 

)) 

Answer 1

把各種參數列表中的相同的參數：

library(mvtnorm) 
u <- list(u1 = c(2,15), u2 = c(5, 18)) 
sigma <- list(sigma1 = matrix(c(3, 0, 0, 9), 2), 
       sigma2 = matrix(c(6, 0, 0, 15), 2)) 
x <- list(c(0.5, 0.5), c(0.6, 0.6)) 
result <- mapply(dmvnorm, x, u, sigma) 
# [1] 1.780234e-07 1.384004e-07 

這相當於：

result <- numeric(length(x)) 
for (i in 1:length(x)) 
    result[i] <- dmvnorm(x[[i]], u[[i]], sigma[[i]])