Databases
StackOverflow2013
Postsdbo
POC array of functions
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POC array of functions
    primarykey
    data
    text
    <p>I have a problem with a series of functions. I have an array of 'return values' (i compute them through matrices) from a single function <strong>sys</strong> which depends on a integer variable, lets say, <strong>j</strong>, and I want to return them according to this <strong>j</strong> , i mean, if i want the equation number <strong>j</strong>, for example, i just write <strong>sys(j)</strong> For this, i used a <strong>for</strong> loop but i don't know if it's well defined, because when i run my code, i don't get the right values. Is there a better way to have an array of functions and call them in a easy way? That would make easier to work with a function in a Runge Kutta method to solve a diff equation.</p> <p>I let this part of the code here: (<strong>c</strong> is just the <strong>j</strong> integer i used to explain before)</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;math.h&gt; int N=3; double s=10.; //float r=28.; double b=8.0/3.0; / * Define functions * / double sys(int c,double r,double y[]) { int l,m,n,p=0; double tmp; double t[3][3]={0}; double j[3][3]={{-s,s,0},{r-y[2],-1,-y[0]},{y[1],y[0],-b}}; //Jacobiano double id[3][3] = { {y[3],y[6],y[9]} , {y[4],y[7],y[10]} , {y[5],y[8],y[11]} }; double flat[N*(N+1)]; // Multiplication of matrices J * Y for(l=0;l&lt;N;l++) { for(m=0;m&lt;N;m++) { for(n=0;n&lt;N;n++) { t[l][m] += j[l][n] * id[n][m]; } } } // Transpose the matrix (J * Y) -&gt; () t for(l=0;l&lt;N;l++) { for(m=l+1;m&lt;N;m++) { tmp = t[l][m]; t[l][m] = t[m][l]; t[m][l] = tmp; } } // We flatten the array to be left in one array for(l=0;l&lt;N;l++) { for(m=0;m&lt;N;m++) { flat[p+N] = t[l][m]; } } flat[0] = s*(y[1]-y[0]); flat[1] = y[0]*(r-y[2])-y[1]; flat[2] = y[0]*y[1]-b*y[2]; for(l=0;l&lt;(N*(N+1));l++) { if(c==l) { return flat[c]; } } } </code></pre> <p>EDIT ----------------------------------------------------------------</p> <p>Ok, this is the part of the code where i use the function</p> <pre><code>int main(){ output = fopen("lyapcoef.dat","w"); int j,k; int N2 = N*N; int NN = N*(N+1); double r; double rmax = 29; double t = 0; double dt = 0.05; double tf = 50; double z[NN]; // Temporary matrix for RK4 double k1[N2],k2[N2],k3[N2],k4[N2]; double y[NN]; // Matrix for all variables /* Initial conditions */ double u[N]; double phi[N][N]; double phiu[N]; double norm; double lyap; //Here we integrate the system using Runge-Kutta of fourth order for(r=28;r&lt;rmax;r++){ y[0]=19; y[1]=20; y[2]=50; for(j=N;j&lt;NN;j++) y[j]=0; for(j=N;j&lt;NN;j=j+3) y[j]=1; // Identity matrix for y from 3 to 11 while(t&lt;tf){ /* RK4 step 1 */ for(j=0;j&lt;NN;j++){ k1[j] = sys(j,r,y)*dt; z[j] = y[j] + k1[j]*0.5; } /* RK4 step 2 */ for(j=0;j&lt;NN;j++){ k2[j] = sys(j,r,z)*dt; z[j] = y[j] + k2[j]*0.5; } /* RK4 step 3 */ for(j=0;j&lt;NN;j++){ k3[j] = sys(j,r,z)*dt; z[j] = y[j] + k3[j]; } /* RK4 step 4 */ for(j=0;j&lt;NN;j++){ k4[j] = sys(j,r,z)*dt; } /* Updating y matrix with new values */ for(j=0;j&lt;NN;j++){ y[j] += (k1[j]/6.0 + k2[j]/3.0 + k3[j]/3.0 + k4[j]/6.0); } printf("%lf %lf %lf \n",y[0],y[1],y[2]); t += dt; } </code></pre>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USDavid Winchester
    1. USDavid Winchester
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. COPlease translate your comments to english before posting next time, as well as improving your code formatting.
      singulars
      1. POC array of functions
      1. USRichard J. Ross III
    2. COOh sorry, i'll consider that in my next posts. Thanks
      singulars
      1. POC array of functions
      1. USDavid Winchester
    3. CODid you really use the letter 'l' as a loop variable? Thats nearly impossible to read or support. I would suggest ignoring the mathematical part of this problem and write a simple use-case/example of the scenario and either debug it yourself or present your question without the complexity of the real world example. There are too many unknowns about what you are asking, and the other responders are latching on to responses which may not answer the actual question.
      singulars
      1. POC array of functions
      1. USPaul Fox
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload