MATLAB: How to generate automatically multiple symbolic values?

MATLAB

i want to generate for 30 values. because i have to store it to array.

 a(1) =  [a1 a2 a3 a4 a5 a6 a7 a8 a9 a10 a11 a12 a13 a14 a15 a16 a17 a18 a19 a20];

strictly i need a1 a2 a3…i don't need a(1), a(2)…. i want it to generate randomly. if i enter length = 5 then generate only

 [a1, a2 ,a3,a4,a5]

Best Answer

a = sym('a', [1 30])

I am not sure what your mention of randomness is? If you want to scramble the order of these then you could use

a = a(randperm(numel(a)));

Related Solutions

MATLAB: Explicit root of symbolic equations

syms d1 d2 d3 d4 d5 d6 h11 h12 h13 h14 h21 h22 h23 h24 h41 h42...
    h45 h46 h51 h52 h55 h56 h61 h62 h65 h66
eq1 = h11*d1+h12*d2+h13*d3+h14*d4 == 0;
eq2 = h21*d1+h22*d2+h23*d3+h23*d4 == 0;
eq3 = d1+d2+d3+d4-d5-d6 == 0;
eq4 = h41*d1+h42*d2-h41*d3-h42*d4-h45*d5-h46*d6 == 0;
eq5 = h51*d1+h52*d2+h51*d3+h52*d4-h55*d5-h56*d6 == 0;
eq6 = h61*d1+h62*d2-h61*d3-h62*d4-h65*d5-h66*d6 == 0;
% Solve for d1...d6
sol_d1 = isolate(eq1,d1)
sol_d2 = isolate(eq2,d2)
sol_d3 = isolate(eq3,d3)
sol_d4 = isolate(eq4,d4)
sol_d5 = isolate(eq5,d5)
sol_d6 = isolate(eq6,d6)

gives:

sol_d1 =
 
d1 == -(d2*h12 + d3*h13 + d4*h14)/h11
 
 
sol_d2 =
 
d2 == -(d1*h21 + d3*h23 + d4*h23)/h22
 
 
sol_d3 =
 
d3 == d5 - d2 - d4 - d1 + d6
 
 
sol_d4 =
 
d4 == -(d3*h41 - d2*h42 - d1*h41 + d5*h45 + d6*h46)/h42
 
 
sol_d5 =
 
d5 == (d1*h51 + d2*h52 + d3*h51 + d4*h52 - d6*h56)/h55
 
 
sol_d6 =
 
d6 == -(d3*h61 - d2*h62 - d1*h61 + d4*h62 + d5*h65)/h66

This is what you wanted to get?

MATLAB: How to match and eliminate those values?

"i am not able to understand this"

Your code:

find(codes~=s))

first creates a logical array with the same size as codes, with 1 in every location where the arrays differ (you can see that the second row is all zero, where the data match exactly):

>> codes~=s
ans =
  0  0  1  1  0  0  1  1  1  1  0  0  1  1  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  1  0  1  0  1  0  1  1  0  1  0  1  0  1  0

You then use find to obtain the linear indices of those 1's. From the above matrix it is clear that the linear indices will be [6,7,10,12,...], but this is easy to check using MATLAB too:

>> find(codes~=s)
ans =
    6
    7
   10
   12
   18
   19
   22
   24
   25
   27
   28
   33
   37
   39
   40
   45

You then use these linear indices to select elements from codes, you can check this yourself too:

codes(6)  =  0
codes(7)  =  1
codes(10) =  1
codes(11) =  1
codes(12) =  1
... etc
codes(40) =  0
codes(45) =  1

and that is your output vector. Interesting, but ultimately not very useful for the task you described.

"how to match and eliminate those values??"

So far two people have advised to use setdiff: why are you not doing this?

Below is a copy of my answer to your earlier question , where I showed you two ways to achieve what you want:

Method one: setdiff:

>> s = [1,1,0,0,0,0,1,1,0,0,1,1,1,1,0,0]
s =
   1   1   0   0   0   0   1   1   0   0   1   1   1   1   0   0
>> c = [1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0;1,1,0,0,0,0,1,1,0,0,1,1,1,1,0,0;1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0]
c =
   1   1   1   1   0   0   0   0   1   1   1   1   0   0   0   0
   1   1   0   0   0   0   1   1   0   0   1   1   1   1   0   0
   1   0   0   1   0   1   1   0   1   0   0   1   0   1   1   0
>> z = setdiff(c,s,'rows')
z =
   1   0   0   1   0   1   1   0   1   0   0   1   0   1   1   0
   1   1   1   1   0   0   0   0   1   1   1   1   0   0   0   0

Note that setdiff can change the order of the rows, unless you use the 'stable' option:

   setdiff(c,s,'stable','rows')

Method two: indexing:

>> x = all(s==c,2);
>> z = c(~x,:)
z =
   1   1   1   1   0   0   0   0   1   1   1   1   0   0   0   0
   1   0   0   1   0   1   1   0   1   0   0   1   0   1   1   0

Best Answer

Related Solutions

MATLAB: Explicit root of symbolic equations

MATLAB: How to match and eliminate those values?

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