r - 将具有三列(日期、参数、结果)的矩阵解析为在指定日期 R 的每个参数都有一列的矩阵

Question

我有一个包含 3 列和 47,772 行的矩阵。行内有 64 个参数。

目前数据框看起来像:

SAMPLE_DATE PARAMETER   RESULT  
8/2/1954    Alkalinity, total as CaCO3(mg/L)    112.5  
8/2/1954    Depth, Secchi disk depth(m) 2.44  
8/2/1954    Nutrient-nitrogen as N(mg/L)    0.87  
8/2/1954    Phosphorus as P(mg/L)   0.001  
8/2/1954    Sulfate as SO4(mg/L)    11  
3/7/1962    Alkalinity, total as CaCO3(mg/L)    140  
3/7/1962    Alkalinity, total as CaCO3(mg/L)    320  
3/7/1962    Alkalinity, total as CaCO3(mg/L)    130  
3/7/1962    Ammonia-nitrogen as N(mg/L) 0.02  
3/7/1962    Ammonia-nitrogen as N(mg/L) 0.26  
3/7/1962    Ammonia-nitrogen as N(mg/L) 0.02  
3/7/1962    Apparent color(PCU) 10  
3/7/1962    Apparent color(PCU) 10
....  

我想把它变成这样的东西:

Date          Alkalinity, total as CaCO3(mg/L)      Depth, Secchi disk depth(m).....etc  
8/2/1954             112.5                                    2.44              ..... etc  

注意:不是每个日期都有每个参数

有什么想法吗？

Answer 1

这是一种方法。我添加了一个“时间”变量，因为存在重复的“SAMPLE_DATE”+“PARAMETER”组合。

library(reshape2)        # for dcast
library(splitstackshape) # for getanID
x2 <- getanID(x, id.vars = c("SAMPLE_DATE", "PARAMETER"))
dcast(x2, .id + SAMPLE_DATE ~ PARAMETER, value.var = "RESULT")
#   .id SAMPLE_DATE Alkalinity, total as CaCO3(mg/L) Ammonia-nitrogen as N(mg/L)
# 1   1    3/7/1962                            140.0                        0.02
# 2   1    8/2/1954                            112.5                          NA
# 3   2    3/7/1962                            320.0                        0.26
# 4   3    3/7/1962                            130.0                        0.02
#   Apparent color(PCU) Depth, Secchi disk depth(m) Nutrient-nitrogen as N(mg/L)
# 1                  10                          NA                           NA
# 2                  NA                        2.44                         0.87
# 3                  10                          NA                           NA
# 4                  NA                          NA                           NA
#   Phosphorus as P(mg/L) Sulfate as SO4(mg/L)
# 1                    NA                   NA
# 2                 0.001                   11
# 3                    NA                   NA
# 4                    NA                   NA

---

如上，但使用“data.table”包:

library(data.table)
packageVersion("data.table")
# [1] ‘1.8.11’
DT <- data.table(x)
DT[, .id := sequence(.N), by = list(SAMPLE_DATE, PARAMETER)]
dcast.data.table(DT, .id + SAMPLE_DATE ~ PARAMETER, value.var="RESULT")

---

如果您不希望重复的组合在单独的行中，则必须先以某种方式聚合数据。