R data.table fread使用没有标题的命名colClasses（例如没有col.names？） [英] R data.table fread using named colClasses without header (e.g. no col.names?)

问题描述

col.names已添加到data.table 1.9.6上，所以问题已经结束，大家都超级开心:)我想我现在可以将所有我的read.csv调用转换为fread调用而不用担心破坏

col.names was added on data.table 1.9.6 so issue is over and everyone super happy :) I think I can now convert all my read.csv calls to fread calls without worries of destruction

1.9.4

由于我们注意到了巨大的性能改进，我正在将read.csv调用导入fread。大多数问题我可以处理，但我已经达到了一个点，我无知，想知道是否有人有一个elegent解决方案。

I'm importing read.csv calls to fread due to HUGE performance improvements we've noticed. Most issues I can handle but I've reached a point where I'm clueless and wonder if anyone has an elegent solution.

我的问题是，我命名colClasses，但输入没有标题（它是一个grep函数），这里是一个愚蠢的例子有意义：

My problem is that I have named colClasses but the input has no header (it's a grep function), here's a silly example to make sense:

males.students <- read.csv(pipe("grep Male students.csv"), 
                           col.names=c("id", "name", "gender"), 
                           colClasses=(id="numeric"))

现在在fread我还想要命名的colClasses但我没有col名称， / p>

now in fread I still want the named colClasses but I have no col names so just using

males.students <- fread("grep Male students.csv"), 
                        colClasses=(id="numeric"))

失败，

未找到colClasses [[1]]中的列名'id'

Column name 'id' in colClasses[[1]] not found

如何解决？是否有计划添加col.names？

How can I fix that? are there plans to add col.names?

推荐答案

在命令行中添加名称：

fread('echo "id,name,gender"; grep Male students.csv', colClasses = c(id='numeric'))

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