在reshape2中使用min或max时,不会出现非遗漏的参数警告 [英] No non-missing arguments warning when using min or max in reshape2
问题描述
当我在reshape2软件包的dcast函数中使用min或max时,收到以下警告。它告诉我什么?我找不到能解释该警告消息的任何内容,我对为什么在使用max时得到警告而不是在使用均值或其他聚合函数时得到警告感到困惑。
I get the following warning when I use min or max in the dcast function from the reshape2 package. What is it telling me? I can't find anything that explains the warning message and I'm a bit confused about why I get it when I use max but not when I use mean or other aggregate functions.
警告消息:
在.fun(.value [0],...)中:没有min的必填参数;返回Inf
Warning message:
In .fun(.value[0], ...) : no non-missing arguments to min; returning Inf
下面是一个可重现的示例:
Here's a reproducible example:
data(iris)
library(reshape2)
molten.iris <- melt(iris,id.var="Species")
summary(molten.iris)
str(molten.iris)
#------------------------------------------------------------
# Both return warning:
dcast(data=molten.iris,Species~variable,value.var="value",fun.aggregate=min)
dcast(data=molten.iris,Species~variable,value.var="value",fun.aggregate=max)
# Length looks fine though
dcast(data=molten.iris,Species~variable,value.var="value",fun.aggregate=length)
#------------------------------------------------------------
# No warning messages here:
aggregate(value ~ Species + variable, FUN=min, data=molten.iris)
aggregate(value ~ Species + variable, FUN=max, data=molten.iris)
#------------------------------------------------------------
# Or here:
library(plyr)
ddply(molten.iris,c("Species","variable"),function(df){
data.frame(
"min"=min(df$value),
"max"=max(df$value)
)
})
#------------------------------------------------------------
推荐答案
您会收到此警告,因为最小值/最大值应用于长度为0的参数的数字。
You get this warning because the min/max are applied to numeric of length 0 argument.
这会重现警告。
min(numeric(0))
[1] Inf
Warning message:
In min(numeric(0)) : no non-missing arguments to min; returning Inf
请注意,对于平均值
,您不会不会得到警告:
Note that for mean
you don't get the warning :
mean(numeric(0))
[1] NaN
这只是一个警告,它对计算没有任何影响。您可以使用 suppressWarnings
抑制它:
It is just a warning that don't have any effect in the computation. You can suppress it using suppressWarnings
:
suppressWarnings(dcast(data=molten.iris,
Species~variable,value.var="value",
fun.aggregate=min))
编辑
上面我只是在回答一个问题:警告的含义是什么?以及为什么我们有这个最小值/最大值而不是均值函数。为什么 dcast
将聚合函数应用于长度为0的向量的问题,它只是一个BUG,您应该与软件包维护者联系。我认为错误来自 dcast
,
EDIT
Above I am just answering the question: What's the meaning of the warning ? and why we have this min/max and not with mean function. The question why dcast
is applying the aggregate function to a vector of length 0, it is just a BUG and you should contact the package maintainer. I think the error comes from plyr::vaggregate
function used internally by dcast
,
plyr::vaggregate(1:3,1:3,min)
Error in .fun(.value[0], ...) :
(converted from warning) no non-missing arguments to min; returning Inf
特别是以下代码行:
plyr::vaggregate
function (.value, .group, .fun, ..., .default = NULL, .n = nlevels(.group))
{
### some lines
....
### Here I don't understand the meaning of .value[0]
### since vector in R starts from 1 not zeros!!!
if (is.null(.default)) {
.default <- .fun(.value[0], ...)
}
## the rest of the function
.....
}
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