[英]How to apply a function that depends on three variables in R?
Im sure a question like this has been asked before.我敢肯定以前有人问过这样的问题。 But Im struggling to find an answer (and to even word the question clearly).但我努力寻找答案(甚至清楚地表达这个问题)。
If I have 2 variables, I want to apply a function to each pair of these variables, where the function depends on a third variable.如果我有 2 个变量,我想将 function 应用于每对这些变量,其中 function 取决于第三个变量。 For example,例如,
If I have some data that looks like this:如果我有一些看起来像这样的数据:
x <- c(1:4)
y <- c(1,2)
n <- seq(1,200, length.out = 100)
Now, imagine I want to apply rnorm
to each of the pairs of x
and y
, where y
would be my mean and x
would be the standard deviation.现在,假设我想将rnorm
应用于每对x
和y
,其中y
是我的平均值, x
是标准差。 But I want to loop through each of these pairs where each value of n
would be my number of observations.但是我想遍历这些对中的每一对,其中n
的每个值都是我的观察次数。
So for example, I was trying a nested loop... the below example doesn't work, but I hope it illustrates what Im trying to achieve:例如,我正在尝试一个嵌套循环......下面的例子不起作用,但我希望它说明了我试图实现的目标:
for(i in 1:2){
for(j in 1:4){
for(k in 1:length(n)){
ans[] <- rnorm(n[k], y[i], x[j])
}
}
}
Any suggestions as to how I could achieve this?关于我如何实现这一目标的任何建议?
using expand.grid使用 expand.grid
z = expand.grid(n,x,y)
apply(z, 1, function(i) rnorm(i[1], i[2], i[3]))
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