重塑数据并强制缺失为零

Question

编辑： 原始数据集可以在这里找到：link

我有一个像这样的矩阵：

data <- matrix(c("a","1","10",
             "b","1","20",
             "c","1","30",
             "a","2","10",
             "b","2","20",
             "a","3","10",
             "c","3","20"),
             ncol=3, byrow=TRUE)

我想重塑为将缺失值强制为零的数据框：

data <- matrix(c("a","1","10",
             "b","1","20",
             "c","1","30",
             "a","2","10",
             "b","2","20",
             "c","2","0",
             "a","3","10",
             "b","3","0",
             "c","3","20"),
             ncol=3, byrow=TRUE)

如何使用 reshape 包做到这一点？ 谢谢

Answer 1

我们可以使用 tidyr 的complete，在稍微转换一下你的数据后：

library(tidyr)
data <- as.data.frame(data)
data$V3 <- as.numeric(as.character(data$V3))
complete(data, V1, V2, fill = list(V3 = 0))

Answer 2

tidyr 更好，但如果你想使用reshape，你可以

library(reshape2)

data2=dcast(data = as.data.frame(data),V1~V2)
data3=melt( data2,measure.vars=colnames(data2)[-1])
data3[is.na(data3)]="0"

Answer 3

在我看来，您正在处理诸如多元时间序列之类的事情。因此，我建议使用适当的时间序列对象。

library(zoo)
res=read.zoo(data.frame(data,stringsAsFactors=FALSE),
         split=1,
         index.column=2,
         FUN=as.numeric)
coredata(res)=as.numeric(coredata(res))
coredata(res)[is.na(res)]=0

这给了

res
#  a  b  c 
#1 10 20 30
#2 10 20 0 
#3 10 0  20

Answer 4

我认为你有一个包含多个类的矩阵是错误的。

首先我将转换为data.frame 或data.table，然后将所有列转换为正确的类型。类似的东西

library(data.table) # V 1.9.6+
# Convert to data.table
DT <- as.data.table(data) 

# Convert to correct column types
for(j in names(DT)) set(DT, j = j, value = type.convert(DT[[j]])) 

然后我们可以使用data.table::CJ 扩展行并将零分配给NA 值

## Cross join all column except the third
DT <- DT[do.call(CJ, c(unique = TRUE, DT[, -3, with = FALSE])), on = names(DT)[-3]]

## Or if you want only to operate on these two columns you can alternatively do
# DT <- DT[CJ(V1, V2, unique = TRUE), on = c("V1", "V2")]

## Fill with zeroes
DT[is.na(V3), V3 := 0]
DT
#    V1 V2 V3
# 1:  a  1 10
# 2:  a  2 10
# 3:  a  3 10
# 4:  b  1 20
# 5:  b  2 20
# 6:  b  3  0
# 7:  c  1 30
# 8:  c  2  0
# 9:  c  3 20