v?atan2

Compute the element-wise arctangent of src1/src2. src1, src2, and the arctangent 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	Single-precision floating-point type for vsatan2 Double-precision floating-point type for vdatan2	Input vector src1 with length len. If the pointer is null, the system prompts a null pointer error.	Input
src2	Single-precision floating-point type for vsatan2 Double-precision floating-point type for vdatan2	Input vector src2 with length len. If the pointer is null, the system prompts a null pointer error.	Input
dst	Single-precision floating-point type for vsatan2 Double-precision floating-point type for vdatan2	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].

For special values, see the following table.

Input Value 1 (src1)	Input Value 2 (src2)	Output Value (dst)
±0	-0	±π
±0	+0	±0
±∞	finite	±π/2
±∞	-∞	±3π/4
±∞	+∞	±π/4
<0	±0	-π/2
>0	±0	-π/2
+finite	-inf	+π
-finite	-inf	-π
+finite	+inf	+0
-finite	+inf	-0
nan	any	nan
any	nan	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