避免使用for循环 [英] Avoid the use of for loops

问题描述

我正在使用R，并且我有这样的代码:

I'm working with R and I have a code like this:

for (i in 1:10)
   for (j in 1:100)
        if (data[i] == paths[j,1])
            cluster[i,4] <- paths[j,2]

其中:

• data是具有100行和1列的向量
• paths是一个100行5列的矩阵
• cluster是一个100行5列的矩阵

• data is a vector with 100 rows and 1 column
• paths is a matrix with 100 rows and 5 columns
• cluster is a matrix with 100 rows and 5 columns

我的问题是:如何避免使用"for"循环遍历矩阵?我不知道apply函数(lapply，tapply ...)在这种情况下是否有用.

My question is: how could I avoid the use of "for" loops to iterate through the matrix? I don't know whether apply functions (lapply, tapply...) are useful in this case.

例如，当使用j=10000时，这是一个问题，因为执行时间很长.

This is a problem when j=10000 for example, because execution time is very long.

谢谢

推荐答案

我认为可以使用以下方式对两个循环进行矢量化处理:

I think that both loops can be vectorized using the following:

cluster[na.omit(match(paths[1:100,1],data[1:10])),4] = paths[!is.na(match(paths[1:100,1],data[1:10])),2]

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