Question

我有一个矢量：

chbin <- seq (from = 0, to = 10, by = 0.02)

我还有另外两个向量，每个向量都有45个值。

chmean
cherr

我需要创建一个数据帧。数据框的每一行应具有45个值，其中第一个值为dnorm(chbin, mean = (chmean[1]), sd = (cherr[1], log=FALSE)，第二个值为dnorm(chbin, mean = (chmean[2]), sd = (cherr[2], log=FALSE)，依此类推至dnorm(chbin, mean = (chmean[45]), sd = (cherr[45], log=FALSE)。即，对于chbin中的每个值，dnorm被计算45次，对于chmean中的每个值和cherr中的对应值计算一次。结果数据帧将具有45列和与chbin中的值相同的行数。

Answer 1

您可以使用以下嵌套for循环：

chbin <- seq (from = 0, to = 10, by = 0.02)
chmean <- seq (from = 1, to = 2, by = 0.02)
cherr <- seq (from = 1, to = 2, by = 0.02)

foo <- data.frame(matrix(0, nrow=length(chbin), ncol=length(chmean)) )

for(i in 1:length(chbin) ){
 for(j in 1:length(chmean) ){
  foo[i,j] <- dnorm(chbin[i], mean = chmean[j], sd = cherr[j], log=FALSE) 
 }
}

Answer 2

mapply可用于解决问题：

chbin <- seq(from = 0, to = 10, by = 0.02)
chmean <- seq(from = 1, to = 2, by = 0.02)
cherr <- seq(from = 1, to = 2, by = 0.02)    

foo <- mapply(function(mean,sd) dnorm(chbin,mean,sd), mean=chmean, sd=cherr)

如何使用向量中的每个值作为平均值来重复R中的dnorm？

2 个答案: