R中使用rSymph的符号矩阵问题答案

【问题标题】：Symbolic matrix problem in R using rSymphR中使用rSymph的符号矩阵问题
【发布时间】：2021-08-30 06:00:02
【问题描述】：

我需要在 R 控制台中使用 rSympy 执行符号矩阵乘法 Ry.Ry。

library(rSymPy)
Ry = matrix(c("c","-s","s","c"),2,2, byrow=1); Ry
########## I convert matrix in R to Python's format
# from https://stackoverflow.com/questions/39820161/handling-symbolic-matrices-in-r-as-in-matlab
# written by jav

mat2py <- function(x){
  str = lapply(1:nrow(x), function(i) 
paste0(x[i,], collapse = ", "))
  str = paste0("Matrix([", paste0("[", 
unlist(str), "]", collapse = ", "), "])")
  return (str)
}
mat2py(Ry)
cat(sympy(mat2py(Ry)), "\n")

得到如下错误信息：

.jcall("RJavaTools", "Ljava/lang/Object;", "invokeMethod", cl, : Traceback (最近一次调用最后一次): File "", line 1、在NameError: name 'c' is not defined

【问题讨论】：

标签： python r matrix-multiplication symbolic-math

【解决方案1】：

仍然收到错误消息。当我执行 cat(sympy("Ry*Ry"), "\n")

.jcall("RJavaTools", "Z", "hasField", .jcast(x, "java/lang/Object"), 中的错误： java.lang.NullPointerException ####################下面是代码#############

library(rSymPy)
str1="c"
str2="-s"
str3="s"
str4="c"
str(str1)
P=matrix(c(str1, str2, str3, str4),2,2, byrow=1); P

Ry<-matrix(nrow=2, ncol=2)
for (i in 1:2){
for (j in 1:2) {
Ry[i,j] = paste0(P[i,j]) # Declare variable in matrix 
first
   }
 }
Ry

mat2py <- function(x){
str = lapply(1:nrow(x), function(i) paste0(x[i,], 
collapse = ", "))
str = paste0("Matrix([", paste0("[", unlist(str), "]", 
collapse = ", "), "])")
return (str)
}

 mat2py(Ry)
 cat(sympy(mat2py(Ry)), "\n")
 cat(sympy("Ry*Ry"), "\n")

【讨论】：

【解决方案2】：

遵循 rSymPy 的文档 - 您是否已经尝试使用此代码？我不熟悉 rSymPy 包，但我认为有必要将变量 c、-s 和 s 声明为 SymPy 变量。

library(rSymPy)
# create a SymPy variable called c
sympy("var('c')")
# create a SymPy variable called -s
sympy("var('-s')")
# create a SymPy variable called s
sympy("var('s')")

# Matrices are stored row by row (unlike R matrices)
cat(sympy("Ry = Matrix([[c,-s], [s,c]])"), "\n")
cat(sympy("Ry*Ry"), "\n")

【讨论】：