Differencial equation of eq "without" variables?

Good day to all of you,

I would like to ask a question about differencial / derivative (don't know the right "syntax" - not an english native speaking person).

I've got an equation like in this pic: http://imgur.com/xc3fuMT

My problem is that I have to do the Diff Eq of bending curve for my thesis but I don't know how to derive that equation if I know everything in it. even the x1 (which is my derivative parameter) I know. It's [0, 2, 4, 6, 8, .. 200] (for example).

If I do it in my paper, it's easy (as shown in the picture) but I don' know how to do it in matlab.

Can anybody help please?

[Son Goku ssj4]

Okay so I had to put all of my variables as "syms".

Is there a way to set it for ALL of the variables all at once? Like

 syms all

? I had to set each one of them (I've got 120 variables)

[Walter Roberson]

There is no way to "syms all". However, you can put multiple variables on one "syms" line

syms x1 x2 pqr17

[Son Goku ssj4]

That's a shame. So if I want to derive a function and then calculate the derivative, the only process for me is:

 1) x = 5 % Need this valus for another calculating

 2) eq = x^2 + x - 5 % Evaluate this equation for making a plot

 3) syms x % I have to derive so put it as syms

 4) eq = x^2 + x - 5 = 0 % Write down once more or just go to step five: eq_D = diff(eq)

 5) eq_D = diff(x^2 + x - 5) -> x + 1
 6) x = 5

 7) eq_D % result for another plot

Or is there some way so that I don't have to put ALL OF MY values as SYMS, --then-- make the diff, --then-- again write values to my variables, --then-- make the result by evaluation?

Consider that I'm using 27 different equations, which every one of them has around 4 variables. So writing: syms F_A F_A1 F_A2 F_A3 F_A4 ... F_C60 is quite a long way to do it. :-)

(I hope it's understandable)

My guess would be something with separate space, but I don't know such a thing yet.

Answer 1

[Walter Roberson]

xvals = 5:.01:7   %for example

syms x
eq = x^2 + x - 5
eq_x = double(subs(eq, x, xvals));
plot(xvals, eq_x);

eq_D = diff(eq, x);
eq_D_x = double( subs(eq_D, x, xvals) );
plot(xvals, eq_D_x);

[Son Goku ssj4]

I'm trying to put all of my variables as "sym" /syms in one script.

I thought a way. Witht the function "who" which will write all variables. But...

 varibl = who'  % this will create vector of variables

 for i = 1 : 1 : length(varibl) % i = 1 .. x (x = number of variables)
 syms varibl(i)   ->   I thought it will do syms varibl(1) syms varibl(2) ...
 end

but for no avail. It will creaty only syms varibl and syms i

Is there any way to put all variables in syms function with this "solution"?