如何使用ddply按组对数据进行子采样? [英] How do I sub sample data by group using ddply?

问题描述

我的数据框的行太多了，无法进行空间相关图分析.相反，我想为每个物种抓取40行，并在该子集上运行相关图.

I've got a data frame with far too many rows to be able to do a spatial correlogram. Instead, I want to grab 40 rows for each species and run my correlogram on that subset.

我编写了一个子集数据框的函数，如下所示:

I wrote a function to subset a data frame as follows:

    samp <- function(dataf)
{
    dataf[sample(1:dim(dataf)[1], size=40, replace=FALSE),]
}

现在我想将此功能应用于更大数据框中的每个物种.

Now I want to apply this function to each species in a larger data frame.

当我尝试类似的东西

culled_data = ddply (larger_data, .(species), subset, samp)

我收到此错误:

Error in subset.data.frame(piece, ...) : 
  'subset' must evaluate to logical

有人知道如何做到这一点吗?

Anyone got ideas on how to do this?

推荐答案

从通话中删除, subset后，它似乎应该可以工作.

It looks like it should work once you remove , subset from your call.

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