v?atan2

Compute the element-wise arc tangent of src1/src2. src1, src2, and the arc tangent are all vectors.

Interface Definition

C interface:

void vsatan2(const int len, const float* src1, const float* src2, float* dst);

void vdatan2(const int len, const double* src1, const double* src2, double* dst);

Fortran interface:

CALL VSATAN2(LEN, SRC1, SRC2, DST);

CALL VDATAN2(LEN, SRC1, SRC2, DST);

Parameters

Parameter	Type	Description	Input/Output
len	Integer	Number of elements in the input vector. If len ≤ 0, the system displays a message indicating that the value of len is invalid.	Input
src1	For vsatan2, src1 is of single-precision floating-point type. For vdatan2, src1 is of double-precision floating-point type.	Input vector src1 with length len. If the pointer is null, the system prompts a null pointer error.	Input
src2	For vsatan2, src2 is of single-precision floating-point type. For vdatan2, src2 is of double-precision floating-point type.	Input vector src2 with length len. If the pointer is null, the system prompts a null pointer error.	Input
dst	For vsatan2, dst is of single-precision floating-point type. For vdatan2, dst is of double-precision floating-point type.	Output vector dst with length len. If the pointer is null, the system prompts a null pointer error.	Output

Return Value

An azimuth from the origin to the point (x, y) is returned for each operation value atan2(y, x), that is, the included angle with reference to the x-axis. The unit of the return value is radian, and the value range is (-π, +π].
If y is ±0 and x is negative or -0, the return value is ±π.
If y is ±0 and x is positive or +0, the return value is ±0.
If y is ±∞ and x is a finite number, the return value is ±π/2.
If y is ±∞ and x is –∞, the return value is ±3π/4.
If y is ±∞ and x is +∞, the return value is ±π/4.
If x is ±0 and y is negative, the return value is -π/2.
If x is ±0 and y is positive, the return value is +π/2.
If x is -∞ and y is a finite positive number, the return value is +π.
If x is -∞ and y is a finite negative number, the return value is -π.
If x is +∞ and y is a finite positive number, the return value is +0.
If x is +∞ and y is a finite negative number, the return value is -0.
If x or y is NaN, the return value is NaN.

Dependencies

C: "kvml.h"

Fortran: "kvml.f03"

Examples

C interface:

    int i, len = 4; 
    float src1[len] = [0.0f, 1.0f, -inf, inf]; 
    float src2[len] = [0.0f, 2.0f, inf, nan]; 
    float* dst = (float*)malloc(sizeof(float) * len); 
    if (dst == NULL) { 
        printf("Malloc Failed!\n"); 
        return 0; 
    } 
    vsatan2(len, src1, src2, dst); 
    /** 
     *  Output dst: 
     *     0.0  0.463647603988647  -0.785398185253143  nan 
     * 
     */

Fortran interface:

    INTEGER :: LEN = 4 
    REAL(4) SRC1(4)  
    REAL(4) SRC2(4) 
    REAL(4) DST(4) 
    DATA SRC1 /1.2, 2.5, -2.4, 3.6/ 
    DATA SRC2 /8.6, -2.5, -12.4, 32.6/ 
    CALL VSATAN2(LEN, SRC1, SRC2, DST) 
    !  
    ! OUTPUT DST: 
    !     0.138639733, 2.35619450, -2.95040822, 0.109983824 
    !

Parent topic: Function Syntax