R - 如何将 2 个成对向量组合成矩阵

Question

鉴于下表:

X = 

        col1    col2    col3
row1    "A"      "A"     "1.0"
row2    "A"      "B"     "0.9"
row3    "A"      "C"     "0.4"
row4    "B"      "A"     "0.9"
row5    "B"      "B"     "1.0"
row6    "B"      "C"     "0.2"
row7    "C"      "A"     "0.4"
row8    "C"      "B"     "0.2"
row9    "C"      "C"     "1.0"

其中 col3 是 col1 和 col2 中实体对之间的相关性度量。

如何构造列名称为 col1、行名称为 col2 且矩阵单元格中的值由 col3 填充的矩阵？

Answer 1

df <- read.table(textConnection('col1    col2    col3
row1    "A"      "A"     "1.0"
row2    "A"      "B"     "0.9"
row3    "A"      "C"     "0.4"
row4    "B"      "A"     "0.9"
row5    "B"      "B"     "1.0"
row6    "B"      "C"     "0.2"
row7    "C"      "A"     "0.4"
row8    "C"      "B"     "0.2"
row9    "C"      "C"     "1.0"'), header=T)

## fetch row/column indices
rows <- match(df$col1, LETTERS)
cols <- match(df$col2, LETTERS)

## create matrix
m <- matrix(0, nrow=max(rows), ncol=max(cols))

## fill matrix
m[cbind(rows, cols)] <- df$col3

m
#     [,1] [,2] [,3]
#[1,]  1.0  0.9  0.4
#[2,]  0.9  1.0  0.2
#[3,]  0.4  0.2  1.0