RWalib C Array Library User Guide > Trigonometric Functions > alibAtan2
  

alibAtan2
Returns the inverse tangent for two arguments, element-wise. The PV-WAVE API for this routine is the ATAN Function.
Prototypes
void alibAtan2f( wvlong m, wvlong n, float *p, float *q, float *r )
void alibAtan2d( wvlong m, wvlong n, double *p, double *q, double *r )
Parameters
m — (Input) The number of elements in the first array operand. A value of 0 indicates that the first operand is a scalar.
n — (Input) The number of elements in the second array operand. A value of 0 indicates that the second operand is a scalar. If both operands are arrays then n must equal m.
*p — (Input) The pointer to the first operand.
*q — (Input) The pointer to the second operand.
*r — (Input/Output) The destination array. On return, array r contains the inverse tangent of arguments p and q, element-wise. By convention, arguments p and q are associated with ordinates and abscissas, respectively. The operation can be done in-place, i.e., r can equal p or q.
Example
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "alib.h"
void main() {
   /* make up some input data for the examples */
   float  f0=1, f1[8]={-1,0,3,1,2,0,-3,-2}, f2[8]={-1,-2,-3,0,2,1,3,0};
   /* make an output array */
   float  f[8];
   printf( "\n\n show scalar f0 and (2,4) matrices f1 and f2" );
      alibinit( NULL, NULL, NULL, NULL );
      alibPrintArrayf( 1, 1, 1, 1, &f0, NULL );
      alibPrintArrayf( 1, 1, 2, 4, f1, NULL );
      alibPrintArrayf( 1, 1, 2, 4, f2, NULL );
   printf( "\n\n show the inverse tangent for f0 and f1, element-wise" );
      alibAtan2f( 0, 8, &f0, f1, f );
      alibPrintArrayf( 1, 1, 2, 4, f, NULL );
   printf( "\n\n show the inverse tangent for f1 and f0, element-wise" );
      alibAtan2f( 8, 0, f1, &f0, f );
      alibPrintArrayf( 1, 1, 2, 4, f, NULL );
   printf( "\n\n show the inverse tangent for f1 and f2, element-wise" );
      alibAtan2f( 8, 8, f1, f2, f );
      alibPrintArrayf( 1, 1, 2, 4, f, NULL );
   printf( "\n\n repeat the operation in-place" );
      alibAtan2f( 8, 8, f1, f2, f2 );
      alibPrintArrayf( 1, 1, 2, 4, f2, NULL );
}
 
Output:
 
 show scalar f0 and (2,4) matrices f1 and f2
 
   1.000e+00
 
  -1.000e+00   0.000e+00   3.000e+00   1.000e+00
   2.000e+00   0.000e+00  -3.000e+00  -2.000e+00
 
  -1.000e+00  -2.000e+00  -3.000e+00   0.000e+00
   2.000e+00   1.000e+00   3.000e+00   0.000e+00
 
 show the inverse tangent for f0 and f1, element-wise
 
   2.356e+00   1.571e+00   3.218e-01   7.854e-01
   4.636e-01   1.571e+00   2.820e+00   2.678e+00
 
 show the inverse tangent for f1 and f0, element-wise
 
  -7.854e-01   0.000e+00   1.249e+00   7.854e-01
   1.107e+00   0.000e+00  -1.249e+00  -1.107e+00
 
 show the inverse tangent for f1 and f2, element-wise
 
  -2.356e+00   3.142e+00   2.356e+00   1.571e+00
   7.854e-01   0.000e+00  -7.854e-01  -1.571e+00
 
 repeat the operation in-place
 
  -2.356e+00   3.142e+00   2.356e+00   1.571e+00
   7.854e-01   0.000e+00  -7.854e-01  -1.571e+00

Version 2017.0
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