套用至两个资料框

本文介绍了套用至两个资料框的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我正在使用R，并且有两个data.frames，A和B.它们都具有6行，但是A具有25000列(基因)，而B具有30列.我想应用带有两个参数f(x,y)的函数，其中x是A的每一列，而y是B的每一列.到目前为止，看起来像这样:

I'm using R, and I have two data.frames, A and B. They both have 6 rows, but A has 25000 columns (genes), and B has 30 columns. I'd like to apply a function with two arguments f(x,y) where x is every column of A and y is every column of B. So far it looks like this:

i = 1
for (x in A){
    j = 1
    for (y in B){
        out[i,j] <- f(x,y)
        j = j + 1
    }
    i = i + 1
}

我对此有两个问题:从我的Python编程中，我联想到跟踪这样的计数器很麻烦，而从我的R编程中，我对for循环感到不安.但是，我不太清楚如何应用apply(甚至我应该应用apply)来解决这个问题，并希望有人能启发我.我现在需要将f()视为原子(实际上是cor.test()).

I have two issues with this: from my Python programming I associate keeping track of counters like this as crufty, and from my R programming I am nervous of for loops. However, I can't quite see how to apply apply (or even if I should apply apply) to this problem and was hoping someone might enlighten me. I need to treat f() as atomic (it's actually cor.test()) for now.

推荐答案

由于您正在使用数据帧，因此使用lapply或sapply进行此操作可能会更快(特别是考虑到数据帧的范围).例如

Since you are using data frames, it might be faster to use lapply or sapply to do this (specially given the scope of your data frames). For example,

x <- data.frame(col1=c(1,2,3,4), col2=c(5,6,7,8), col3=c(9,10,11,12))
y <- data.frame(col1=c(1,2,3,4), col2=c(5,6,7,8))
bl <- lapply(x, function(u){
   lapply(y, function(v){
       f(u,v) # Function with column from x and column from y as inputs
   })
})
out = matrix(unlist(bl), ncol=ncol(y), byrow=T)

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