R-多个嵌套循环 [英] R - multiple nested loops

问题描述

我正在尝试编写一个嵌套循环代码，以模拟具有101行的数据帧中的10列数据.第一行数据已分配为起始值.由于我的矩阵r是根据随机法线生成的，因此每列都应该不同.但是，每列中的结果值完全相同.为循环索引提供一些背景信息:

I am trying to write a nested loop code to simulate 10 columns of data in a data frame with 101 rows. The first row of data has been assigned as starting values. Each column should be different as my matrix r is generated from random normals; however, the resulting values in each column are exactly the same. To give some context for the looping indices:

tmax=100; ncol(pop_sims) = 12 (so a total of 10 iterations, 3-12); ncol(r) = 10

for (i in 1:tmax){
 for (j in 3:ncol(pop_sims)){
   for(k in 1:ncol(r)){

   if (pop_sims[i,j]*exp(r[i,k]) <2) {
    pop_sims[i+1,j]<- 0} 
  else {
      pop_sims[i+1,j] <- pop_sims[i,j]*exp(r[i,k])}
}}} 

任何想法都会受到赞赏.

Any thoughts would be appreciated.

更新:我没有使用多个循环，而是省略了矩阵r的使用，简化了我的循环.

UPDATE: Instead of working with the multiple loops, I omitted the use of the matrix r and simplified my loops.

for (i in 1:tmax){
 for (j in 1:10){

  if (pop_sims[i,j]*exp(r[i,j]) <2) {
    pop_sims[i+1,j]<- 0} 
  else {
      pop_sims[i+1,j] <- pop_sims[i,j]*exp(rnorm(1,mean=0.02, sd=0.1))}
}}

推荐答案

循环几乎从来都不是在R中完成任务的最佳方法.听起来好像您想将一些初始值乘以随机数的累加乘积，然后将其存储为矩阵的列. cumprod是如何在R中获得累积积:

Looping is almost never the best way to accomplish a task in R. It sounds like you want to multiply some initial value by the cumulative product of random numbers, and store this as the columns of a matrix. cumprod is how to get a cumulative product in R:

tmax = 100
initial.row = 1:10
rbind(initial.row, sapply(initial.row,
                          function(x) x*cumprod(exp(rnorm(tmax-1, mean=.02, sd=.1)))))

#                 [,1]       [,2]      [,3]     [,4]      [,5]      [,6]       [,7]       [,8]      [,9]     [,10]
# initial.row 1.000000   2.000000  3.000000 4.000000  5.000000  6.000000   7.000000   8.000000  9.000000 10.000000
#             1.211479   2.483438  3.376012 3.684407  5.611144  5.689530   6.115748   7.809380  8.364223 10.748108
#             1.221254   2.832064  3.500622 3.417095  5.047067  5.706181   6.445985   9.031854  8.125584 10.115107
#             1.350398   3.002284  3.723416 3.581471  5.121880  7.300373   8.008373  10.679728  7.167270 10.310810
#             1.269193   2.883153  3.546245 3.160029  5.312947  7.983395   6.986608  11.226517  7.166026  9.195459
#             ...

这篇关于R-多个嵌套循环的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！