如果在Julia中生成矢量，则生成微分方程 [英] Generate DifferentialEquations ifrom a vector in Julia

问题描述

我创建了一个向量，该向量将微分方程的字符串连接起来，格式正确，可用于茱莉亚的差分运算法则(即f(du，u，p，t):

I have created a vector which concatenates strings of differential equations that are in the correct format to be used be the differeq ode sovler in Julia (i.e, f(du,u,p,t):

Combine <- c("du[1] = - 1*0.4545*(u[1]^1) - 1*27000000*(u[4]^1)*(u[1]^1)", 
"du[2] = - 1*3100000000*(u[2]^1)*(u[4]^1)", "du[3] = - 1*33000*(u[3]^1)*(u[4]^1)", 
"du[4] =2*0.4545*(u[1]^1) - 1*3100000000*(u[2]^1)*(u[4]^1) - 1*33000*(u[3]^1)*(u[4]^1) - 1*27000000*(u[4]^1)*(u[1]^1) - 1*8500000*(u[4]^1)*(u[5]^1) - 1*390000000*(u[4]^1)*(u[6]^1)", 
"du[5] = - 1*8500000*(u[4]^1)*(u[5]^1)", "du[6] = - 1*390000000*(u[4]^1)*(u[6]^1)"

我的问题是如何使用JuliaCall:Julia_eval评估这些表达式?我知道，如果我明确包含表达式，则ODE求解器可以正常工作，但是如果我仅使用Combine [i]，则会遇到错误，因为我正在调用全局变量.

My question is how can I evaluate these expressions using JuliaCall:Julia_eval? I know that if I explicitly include the expressions the ODE solver works correctly, but if I just use Combine[i] I run into an error because I am calling a global variable.

f <- JuliaCall::julia_eval("
     function f(du,u,p,t)
                                  du[1] = - 1*0.4545*(u[1]^1) - 1*27000000*(u[4]^1)*(u[1]^1)
                                  du[2] = - 1*3100000000*(u[2]^1)*(u[4]^1)
                                  du[3] = - 1*33000*(u[3]^1)*(u[4]^1)
                                  du[4] = 2*0.4545*(u[1]^1) - 1*3100000000*(u[2]^1)*(u[4]^1) - 1*33000*(u[3]^1)*(u[4]^1) - 1*27000000*(u[4]^1)*(u[1]^1) - 1*8500000*(u[4]^1)*(u[5]^1) - 1*390000000*(u[4]^1)*(u[6]^1)
                                  du[5] = - 1*8500000*(u[4]^1)*(u[5]^1)
                                  du[6] = - 1*390000000*(u[4]^1)*(u[6]^1)
end")

有什么办法可以解决此问题?我尝试取消列出"Combine"的列表，并在每行末尾添加\ n来创建单个字符串，但这未成功.理想的情况是，我可以从全局环境中调用向量，并由ODE求解器对其进行分析，如下所示(我知道这不能像这样工作):

Is there any way to work around this? I have tried unlisting "Combine" and creating a single string with \n included at the end of each line but this was unsuccessful. It would be ideal if I could call in the vector from the global environment and have that analyzed by the ODE solver, something like below ( i know this cant work like this):

f <- JuliaCall::julia_eval("
     function f(du,u,p,t)
         Combine[i]
end")

推荐答案

如@jverzani所述，

As @jverzani mentioned,

sprintf("function f(du,u,p,t)\n%s\nend", paste(Combine, collapse="\n"))

在R中构建所需的字符串.如果您JuliaCall::julia_eval那，那么您就完成了.其他任何事情都完全过分复杂，并且无论如何也不会进行优化，因此，我不建议您尝试在此处采用的其他路径.

builds the string in R that you want. If you JuliaCall::julia_eval that, then you're done. Anything else is completely over-complicated, and will also be less optimized anyways, and so I would no recommend the other paths you are trying to take here.

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