R如何计算跨数据帧多列的值的出现次数，并将特定值的按列计数保存为新行？ [英] R How to count occurrences of values across multiple columns of a data frame and save the columnwise counts from a particular value as a new row?

问题描述

我有一个很大的数据框（大约1,000行和30,000列），看起来像这样：

I have a large data-frame (approx 1,000 rows and 30,000 columns) that looks like this:

   chr pos  sample1 sample2 sample3 sample 4
    1 5050    1       NA      0       0.5
    1 6300    1       0       0.5     1
    1 7825    1       0       0.5     1
    1 8200    0.5     0.5     0       1

其中，在给定的 chr和 pos下，给定样本的值可以采用0、0.5， 1，或NA。我要执行大量查询，这些查询需要根据每个样本的值摘要对数据框进行设置和排序。

where at a given "chr"&"pos" the value for a given sample can take the form of 0, 0.5, 1, or NA. I have a large number of queries to perform that will require subsetting and ordering the data frame based on summaries of the values for each sample.

我想获得一个计数每列给定值（例如0.5）的出现次数，并将其另存为我的数据框中的新行。我的最终目标是能够使用新行的值对数据框的列进行子集和/或排序。我已经看到过类似的关于计数出现次数的问题，但是我似乎找不到/认识到一种解决方案，可以同时在所有列上执行此操作，并将特定值的列计数保存为新行。

I would like to get a count of the number of occurrences of a given value (e.g. 0.5) for each column, and save that as a new row in my data frame. My ultimate goal is to be able to use the values of the new row to subset and/or order the columns of my data frame. I've seen similar questions about counting occurrences, but I can't seem to find/recognize a solution to doing this across all columns simultaneously and saving the column-wise counts for a particular value as a new row.

推荐答案

您可以将函数应用于data.frame的所有列。假设您要计算data.frame d的每一列中的 A数。d

you can apply a function to all the column of you data.frame. Suppose you want to count the number of 'A' in each column of the data.frame d

#a sample data.frame
    L3 <- LETTERS[1:3]
     (d <- data.frame(cbind(x = 1, y = 1:10), fac = sample(L3, 10, replace = TRUE)))



# the function you are looking for
    apply(X=d,2,FUN=function(x) length(which(x=='A')))

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