Question

我想在R中象征性地添加两个矩阵P和Q.我使用＆＃34; rSymPai＆＃34;库函数。然后我怎样才能找到等于P + Q的X.

/authorize

Answer 1

包裹＆＃39; rSymPy＆＃39;只是Python的SymPy包的包装器。 This is the documentation for matrices

您需要Python / SymPy中的以下代码（使用SymPy live尝试）：

P = Matrix([['P1','P2'],['P3','P4']])
Q = Matrix([['Q1','Q2'],['Q3','Q4']])
Result = P + Q

在R中，rSymPy函数sympy(...)将Python代码作为字符串，因此您希望在R中生成以下字符串：

"P = Matrix([['P1','P2'],['P3','P4']])"
"Q = Matrix([['Q1','Q2'],['Q3','Q4']])"

您可以通过R字符串操作从问题中的变量P和Q生成此字符串。之后，您应该能够将它们与R sympy函数一起使用（无法测试最后三行，因为我没有在此机器上安装Python和SymPy）

library(rSymPy)
# Copied from Question
P<-matrix(nrow=2, ncol=2)
for (i in 1:2){
  for (j in 1:2) {
    P[i,j] = paste0("P", i, j) 
  }
}
P
##      [,1]  [,2] 
## [1,] "P11" "P12"
## [2,] "P21" "P22"
Q<-matrix(nrow=2, ncol=2)
for (i in 1:2){
  for (j in 1:2) {
    Q[i,j] = paste0("Q", i, j) 
  }
}
Q
##      [,1]  [,2] 
## [1,] "Q11" "Q12"
## [2,] "Q21" "Q22"
# -----------------------------------
makeSymPyMatrix <- function(name, mat){
  dim <- dim(mat) # needed to restore matrix dimensions
  # Add the single quotes
  mat <- Q
  mat <- sub('(.*)',"'\\1'",mat)
  # Add the inner commas
  mat <- apply(mat, 1, function(row){paste(row, collapse = ',')})
  # Add the inner brackets
  mat <- sub('(.*)',"[\\1]",mat)
  # Add the outer commas
  mat <- paste(mat, collapse = ',')
  # Add the outer brackets
  mat <- sub('(.*)',"[\\1]",mat)
  # Add the Matrix function
  mat <- sub('(.*)',"Matrix(\\1)",mat)
  return(mat)
}
# See what this function returns
makeSymPyMatrix(P)
## "Matrix([['P11','P12'],['P21','P22']])"
Pvar <- sympy(makeSymPyMatrix(P))
Qvar <- sympy(makeSymPyMatrix(Q))
Pvar + Qvar

R中的符号矩阵加法

1 个答案: