将符号数学 (sym) 的输出转换为浮点数 [英] Convert output from symbolic math (sym) to float

问题描述

我的问题类似于这个问题 但我认为它更笼统.
我使用 Matlab 的符号数学工具箱来解方程:

My question is similar to this question but I believe it to be more general.
I use Matlab's symbolic math toolbox to solve an equation:

MAZ = 0.5;
MAU = 1.0;
XI = 1.0;
ALPHA = 2.0;

DRG = 0.5;
SRG = 1.0;

PHI = 1 / (2 * MAU);

syms L;

f = 1 - DRG - sqrt(1 + (ALPHA * XI - L / (2 * XI * PHI) ) ^ 2 ) / ...
    sqrt(1 + (ALPHA * XI) ^ 2) + L / (4 * PHI * SRG * sqrt(1 + (ALPHA * XI)^2));

a = solve(f,L,'Real',true);

答案是:

a =
5^(1/2)/3 + (10*((4*5^(1/2))/25 + 6/25)^(1/2))/3 + 8/3
5^(1/2)/3 - (10*((4*5^(1/2))/25 + 6/25)^(1/2))/3 + 8/3  

如何将 a 的这些表达式(不包含任何符号表达式)自动转换为浮点数，以便稍后在我的代码中访问它们?

How do I automatically convert these expressions for a - which do not contain any symbolic expressions - to floats so that I can access them later in my code?

推荐答案

Matlab 的符号数学工具箱包含一个名为 double.
此函数将 solve 函数的结果 - 这是一个 sym - 转换为双精度:

Matlab's symbolic math toolbox contains a function called double.
This function converts the result of the solve function - which is a sym - to a double:

double(a)

ans =

      5.98921078320145
     0.834834535131742

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