Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Here's C++ for linear and quadratic interpolation.<br> <code>interp1( 5.3, a, n )</code> is a[5] + .3 * (a[6] - a[5]), .3 of the way from a[5] to a[6];<br> <code>interp1array( a, 1000, b, 1500 )</code> would stretch <code>a</code> to <code>b</code>.<br> <code>interp2( 5.3, a, n )</code> draws a parabola through the 3 nearest points a[4] a[5] a[6]: smoother than interp1 but still fast.<br> (Splines use 4 nearest points, smoother yet; if you read python, see <a href="http://advice.mechanicalkern.com/question/22/basic-spline-interpolation-in-a-few-lines-of-numpy" rel="noreferrer">basic-spline-interpolation-in-a-few-lines-of-numpy</a>.</p> <pre><code>// linear, quadratic interpolation in arrays // from interpol.py denis 2010-07-23 July #include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; // linear interpolate x in an array // inline float interp1( float x, float a[], int n ) { if( x &lt;= 0 ) return a[0]; if( x &gt;= n - 1 ) return a[n-1]; int j = int(x); return a[j] + (x - j) * (a[j+1] - a[j]); } // linear interpolate array a[] -&gt; array b[] void inter1parray( float a[], int n, float b[], int m ) { float step = float( n - 1 ) / (m - 1); for( int j = 0; j &lt; m; j ++ ){ b[j] = interp1( j*step, a, n ); } } //.............................................................................. // parabola through 3 points, -1 &lt; x &lt; 1 float parabola( float x, float f_1, float f0, float f1 ) { if( x &lt;= -1 ) return f_1; if( x &gt;= 1 ) return f1; float l = f0 - x * (f_1 - f0); float r = f0 + x * (f1 - f0); return (l + r + x * (r - l)) / 2; } // quadratic interpolate x in an array float interp2( float x, float a[], int n ) { if( x &lt;= .5 || x &gt;= n - 1.5 ) return interp1( x, a, n ); int j = int( x + .5 ); float t = 2 * (x - j); // -1 .. 1 return parabola( t, (a[j-1] + a[j]) / 2, a[j], (a[j] + a[j+1]) / 2 ); } // quadratic interpolate array a[] -&gt; array b[] void interp2array( float a[], int n, float b[], int m ) { float step = float( n - 1 ) / (m - 1); for( int j = 0; j &lt; m; j ++ ){ b[j] = interp2( j*step, a, n ); } } int main( int argc, char* argv[] ) { // a.out [n m] -- int n = 10, m = 100; int *ns[] = { &amp;n, &amp;m, 0 }, **np = ns; char* arg; for( argv ++; (arg = *argv) &amp;&amp; *np; argv ++, np ++ ) **np = atoi( arg ); printf( "n: %d m: %d\n", n, m ); float a[n], b[m]; for( int j = 0; j &lt; n; j ++ ){ a[j] = j * j; } interp2array( a, n, b, m ); // a[] -&gt; b[] for( int j = 0; j &lt; m; j ++ ){ printf( "%.1f ", b[j] ); } printf( "\n" ); } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POStretching out an array
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USdenis
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POStretching out an array
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI haven't thoroughly tested this code, so I can't vouch for its correctness, but this is exactly the kind of answer I was looking for. Thanks!
      singulars
      1. PO
      1. UStwk
    2. COYou're welcome. If it works, tell the boss; if not, tell me
      singulars
      1. PO
      1. USdenis
 

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