MATLAB: Expression or statement is incomplete or incorrect” whit NL-function some one can help me to find the problem

i have some error message "Expression or statement is incomplete or incorrect"

whit NL-function

some one can help me to find the problem

 function dx=systfun(t,x)
 dx(1) = ((g*A)/x(4))*[x(3)-Zmax_CE-(p0/(rho*g))-(alpha*x(4)*x(1)^2)];
 dx(2) = ((g*A)/(L_CFco-x(4)))*[(ps/(rho*g))-x(3)+(1/(2*g*A^2))-(alpha*(L_CFco-x(4)))*x(2)^2];
 dx(3)= ((-a_CF)^2/(g*a*x(4)))*[x(1)-x(2)+x(5)*sqrt(x(3)-Zi-(po/(rho*g)))]
 dx(4)=0;
 dx(5)=0;
 [ti,xi]= ode45('systfun',[0 4],[20 20  0 0 0]):
 plot(ti,xi,(:,1);'r')

thx ! 🙂

Best Answer

Your ode45 call ends with a colon instead of a semicolon

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MATLAB: How can i create a loop or function

An easy way to detect groups of values is using diff and cumsum.

Then you could use accumarray, which is intended for exactly this kind of operation. Here is a simple example, where each run of identical digits in A is used to sum the values in B (e.g. the first run of A (the nines) sum the first B values [1,2,3] to give six:

>> A = [9,9,9,1,2,2,1,1]';
>> B = [1,2,3,4,5,6,7,8]';
>> X = cumsum([1;0~=diff(A)]);
>> accumarray(X,B)
ans =
     6
     4
    11
    15

If you would prefer to group by value rather then by runs of one values, then you can use unique:

>> [C,~,Y] = unique(A);
>> accumarray(Y,B)
ans =
    19
    11
     6
>> C
C =
     1
     2
     9

Note in this case the ones are summed together, even though they occur in two different runs in A.

MATLAB: Getting error as Matrix dimensions must agree.” can someone help me resolve this

You have

dE_omega_dz(1:length(E_omega)/2) = fft(1i*conj(E1_t).*E2_t.*exp(1i*Dk.*z) ...
    + 1i*2*pi*n_2*I0*L_NL/l*(abs(E1_t.^2 + ...
    2*abs(E2_t.^2)).*E1_t));

This is in a loop in which you are doing

Dk(j)=(deltak);

where you are incrementing j for each iteration of the for Ez loop. Therefore after the first iteration of for Ez, Dk is not a scalar, and the 601 x 1 expression that you get from 1i*conj(E1_t).*E2_t is being .* by a 1 * j variable. In R2016a and earlier that is an error. In R2016b and later, it is permitted and would mean the same thing as if you had used

bsxfun(@times, 1i*conj(E1_t).*E2_t, exp(1i*Dk.*z)

producing a 601 x j result -- a size that is increasing in each iteration of the for Ez loop. But the output size dE_omega_dz(1:length(E_omega)/2) is fixed, leading to a problem of trying to output the wrong amount of information.

Perhaps you should be indexing Dk(j) in the statement.

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MATLAB: How can i create a loop or function

MATLAB: Getting error as Matrix dimensions must agree.” can someone help me resolve this

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