r - 分组、汇总和转置
问题描述
我有一个看起来像这样的数据框:
ctgroup (dataframe)
Camera Trap Name Animal Name a_sum
1 CAM27 Chicken 1
2 CAM27 Dog 1
3 CAM27 Dog 4
4 CAM28 Cat 3
5 CAM28 Dog 22
6 CAM28 Dog 1
*a_sum = 摄像机记录的动物数量
所以基本上我想 - 按 2 个字段(相机陷阱名称,科学名称)分组,然后计算“a_sum”列中的记录数,然后转置数据以便 Animal. 名称变为列,相机陷阱命名我的行。我想在列中显示所有动物名称,如果没有可用数据,则为 0,即,
Camera trap name Dog Cat Wolf Chicken
CAM28 23 4 1 4
CAM27 5 0 0 4
我尝试使用以下代码
dcast (ctgroup, Camera.Trap.name + Animal.name, value.var = "a_sum")
我收到以下错误:
In dcast(ctgroup, Camera.Trap.name + Scientific.name, value.var = "a_sum") :
The dcast generic in data.table has been passed a grouped_df and will attempt to redirect to the reshape2::dcast; please note that reshape2 is deprecated, and this redirection is now deprecated as well. Please do this redirection yourself like reshape2::dcast(ctgroup). In the next version, this warning will become an error.
我认为我知道的不够多,无法构建正确的代码来执行这项工作。
解决方案
使用 data.table ...
# Load data.table.
require(data.table)
# Create data.set.
df <- data.frame(Camera = c("CAM27", "CAM27", "CAM27", "CAM28", "CAM28", "CAM28"),
Animal = c("Chicken", "Dog", "Dog", "Cat", "Dog", "Dog"),
a_sum = c(1, 1, 4, 3, 22, 1))
# Set the data.frame as a data.table.
setDT(df)
# Cast by `Camera` and `Animal` and sum `a_sum`.
dcast(df, Camera ~ Animal, value.var = "a_sum", fun.aggregate = sum)
# Camera Cat Chicken Dog
# 1: CAM27 0 1 5
# 2: CAM28 3 0 23
# If you want to coerce back to a data.frame.
setDF(df)
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