R :: bigmemory - 如何创建字符big.matrix？ [英] R::bigmemory - how to create character big.matrix?

问题描述

我尝试在 R 中使用 bigmemory 包，我一开始就陷入困境。我这样做：

I try to use bigmemory package in R and I'm stuck in the very beginning. I do:

temp <- matrix(paste("a",1:10), 5, 2)

并获得一个字符矩阵。没关系。但我尝试：

and get a character matrix. That's OK. But then I try:

x <- as.big.matrix(temp, type="char")

，我得到一个填充了NA的矩阵，并显示以下消息：

and I get a matrix full of NA and the following message:

Assignment will down cast from double to char
Hint: To remove this warning type:  options(bigmemory.typecast.warning=FALSE)
Warning messages:
1: In as.big.matrix(temp, type = "char") : Casting to numeric type
2: In matrix(as.numeric(x), nrow = nrow(x), dimnames = dimnames(x)) :
NAs introduced by coercion
3: In SetElements.bm(x, i, j, value) :

我不知道发生了什么，但它看起来big.matrix试图将所有我的文本转换为数字，尽管 type =char。如何使它工作？

I'm not sure what's going on but it looks big.matrix tries to convert all my texts in to numbers despite type = "char". How to make it work?

推荐答案

这是一个误解 - big.matrix对象只存储数字数据类型。 'char'类型是一种C ++数据类型，用于存储表示ASCII字符代码（单个字符，而不是字符串）的整数值。要将字符串存储在big.matrix中，您必须将字符串重新编码为数字值（或转换为因子，然后再转换为数字值）。

This is a bit of a misnomer - big.matrix objects only store numeric data types. The 'char' type is a C++ data type used to store integer values that represent ASCII character codes (a single character, not a character string). To store character strings in a big.matrix, you'll have to re-code the strings as numeric values (or convert to factors, then to numeric values).

如果你需要在一个非常大的数据集中存储字符数据，你可能需要查看'ff'包。在我的经验中，它有一个陡峭的学习曲线，文档有点缺乏，但它有这个功能。

If you need to store character data in a very large data set, you may want to look into the 'ff' package. In my experience it has a steep learning curve and the documentation is somewhat lacking, but it does have that functionality.

有关处理大型数据集的更多详细信息，请查看CRAN任务视图： http://cran.r-project.org/web/views/ HighPerformanceComputing.html

For further details on dealing with large data sets, you can check out the CRAN Task View here: http://cran.r-project.org/web/views/HighPerformanceComputing.html

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