keeping equations in different formats

Hello All.

I have a problem. In my project I have three equations which in times I use with symbolic analysis and some times with numerical values. The problem is that I cannot keep the equations as syms due to the following reasons:

1. I need to always change update the syms in different parts of the code and functions 2. Using subs or eval commands take a lot of time mainly when I use loops to change the values.

Is there a way that I could have the equations saved and call them at symbolic form or numerical form and change the variables without using subs/eval?

Thanks!

Gil,

[José-Luis]

How about encapsulating and using functions?

[Gil Maor]

Thanks for your reply!

I did not understand your suggestions, can you please elaborate?

Thanks!

[José-Luis]

Ok, but could you please provide an example of what you mean. I am having a hard time understanding exactly what you are trying to achieve.

[Gil Maor]

Hi,

lets say I have an equation D=A+B+2C=4

I want a way that I could call this equation as symbolic so I could drevive, for example diff(D,C)=....

and in another time I could just say that A=1 D=2 (without subs commnad) because the subs command works very slow and if I want to change values in a loop it take a lot of time ( 5 min..) since my original equation is very big.

At the moment I copy&paste of the equation when used to in a loop.

I hope I'm clear enough.

Gil,

[Stephen23]

"D=A+B+2C=4"

D=4

[Gil Maor]

Thanks Stephen

I did not understand how to place values in the variables

Gil,

[Karan Gill]

If you want to save/load equations, then use MAT files: https://www.mathworks.com/help/matlab/matlab_env/save-load-and-delete-workspace-variables.html

Of course, that won't work if your numeric values keep changing. You'll have to use subs. Can you provide an example where subs is too slow?

[Gil maor]

Hi Karan, Thanks for your reply.

As for the slowness of subs, this was my doing, I have forgotten to place 'double' in front of the 'subs' so the result was an array of sym...

For advice regrading save , load for the equation object!

Thanks!

Gil,

Answer 1

[Gil maor]

Thanks All.

Problems solved using sym('avr') when ever calling on the equatiobs

Thanks ALL!!

Answer 2

[Walter Roberson]

I suggest that you could keep a struct, one field of which is the symbolic form, and another is the result of calling matlabFunction to transform the symbolic form to a function handle for numeric work.