在R中，如何使向量Y的分量来源于正态分布？

Question

I am a novice in R programming.

I would like to ask experts here a question concerning a code of R.

First, let a vector x be c(2,5,3,6,5)

I hope to make another vector y whose i-th component is derived from N(sum(x[1]:x[i]),1)

(ie the i-th component of y follows normal distribuion with variance 1 and mean summation from x[1](=2) to x[i] (i=1,2,3,4,5) )

For example, the third component of y follows normal distribuion with mean x[1]+x[2]+x[3]=2+5+3=10 and variance 1

I want to know a code of R making the vector y described above "without using repetition syntax such as for, while, etc."

Since I am a novice of R programming and have a congenitally poor sense of computational statistics, I don't seem to hit on a ingenious code of R at all.

Please let me know a code of R making a vector explained above without using repetition syntax such as for, while, etc.

Previously, I should like to thank you very much heartily for your mindful answer.

Answer 1

You can do

rnorm(length(x), mean = cumsum(x), sd = 1)

rnorm is part of the family of functions associated with the normal distribution *norm . To see how a function with a known name works, use

help("rnorm") # or ?rnorm

cumsum takes the cumulative sum of a vector.

Finding functionality

In R, it's generally a safe bet that most functionality you can think of has been implemented by someone already. So, for example, in the OP's case, it is not necessary to roll a custom loop.

The same naming convention as *norm is followed for other distributions, eg, rbinom . You can follow the link at the bottom of ?rnorm to reach ?Distributions , which lists others in base R.

If you are starting from scratch and don't know the names of any related functions, consider using the built-in search tools, like:

help.search("normal distribution") # or ??"normal distribution"

If this reveals nothing and yet you still think a function must exist, consider installing and loading the sos package, which allows

findFn("{cumulative mean}")         # or ???"{cumulative mean}"
findFn("{the pareto distribution}") # or ???"{the pareto distribution}"

Beyond that, there are other online resources, like Google, that are good. However, a question about functionality on Stack Overflow is a risky proposition, since it will not be received well (downvoted and closed as a "tool request") if the implementation of the desired functionality is nonexistent or unknown to folks here. Stack Overflow's new "Documentation" subsite will hopefully prove to be a resource for finding R functions as well.