Question

我有两个不同维度的数据框，一个包含观察结果，另一个包含与算术结果相关的常数。我想做的是从df2中选择适当的常量，用于df1中的行方式观察，以产生df3。

我附上了样本数据和一个简单的等式：

# df1 with annual observation data from different commodities

df1 <- data.frame(Region = c("Europe", "Asia", "N.Amer", "Africa"), 
                  Item = c("Wheat", "Barley", "Oats", "Rice"), 
                  Year = c(1961, 1961, 1961, 1961), 
                  Production = c(2000, 1000, 1500, 500), 
                  Imports = c(1000, 200, 3000, 100), 
                  Stock.Var = c(-100, 300, 50, 0), 
                  Exports = c(250, 150, 100, 200))

#df2 with constants for losses by commodity in different regions

df2 <- data.frame(Area = c("Asia", "N.Amer", "Europe", "Africa"),
                  Item = c("Wheat", "Oats", "Rice", "Barley"), 
                  LF1 = c(0.02, 0.1, 0.15, 0.05))

# df3 would contain the outputs from calculating losses from df1 by df2 by  row
# Equation: L1 = (Production + Imports + Stock.Var - Exports) * LF1

等式中LF1的值取自df2，基于项目＆amp; df1中的区域名称。

df1的完整大小是几十万行乘16列; df2大约是150行乘20列。

Answer 1

可以使用dplyr inner_join和mutate完成此操作：

library(dplyr)
df1 %>% inner_join(df2, by = c(Region = "Area", "Item")) %>%
    mutate(L1 = (Production + Imports + Stock.Var - Exports) * LF1)

如果你宁愿坚持基础R，你可以使用merge：

m <- merge(df1, df2, by.x = c("Region", "Item"), by.y = c("Area", "Item"))
m$L1 <- (m$Production + m$Imports + m$Stock.Var - m$Exports) * m$LF1

R如何从一个数据帧应用选择变量以在另一个数据帧上应用行方程

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