info mathgl

6.7 Change data

These functions change the data in some direction like differentiations, integrations and so on. The direction in which the change will applied is specified by the string parameter, which may contain ‘x’, ‘y’ or ‘z’ characters for 1-st, 2-nd and 3-d dimension correspondengly.

Method on mglData (C++, Python): void CumSum (const char *dir)
C function: void mgl_data_cumsum (HMDT dat, const char *dir): Cumulative summation of the data in given direction or directions.

Method on mglData (C++, Python): void Integral (const char *dir)
C function: void mgl_data_integral (HMDT dat, const char *dir): Integrates (like cumulative summation) the data in given direction or directions.

Метод класса mglData (C++, Python): void Diff (const char *dir)
Функция С: void mgl_data_diff (HMDT dat, const char *dir): Differentiates the data in given direction or directions.

Метод класса mglData (C++, Python): void Diff (const mglData &x, const mglData &y)
Метод класса mglData (C++, Python): void Diff (const mglData &x, const mglData &y, const mglData &z)
Функция С: void mgl_data_diff_par (HMDT dat, const HMDT x, const HMDTy, const HMDTz): Differentiates the data specified parametrically in direction x with y, z=constant. Parametrical differentiation uses the formula (for 2D case): da/dx = (a_j*y_i-a_i*y_j)/(x_j*y_i-x_i*y_j) where a_i=da/di, a_j=da/dj denotes usual differentiation along 1st and 2nd dimensions. The similar formula is used for 3D case. Note, that you may change the order of arguments – for example, if you have 2D data a(i,j) which depend on coordinates {x(i,j), y(i,j)} then usual derivative along ‘x’ will be Diff(x,y); and usual derivative along ‘y’ will be Diff(y,x);.

Метод класса mglData (C++, Python): void Diff2 (const char *dir)
Функция С: void mgl_data_diff2 (const char *dir): Double-differentiates (like Laplace operator) the data in given direction.

Метод класса mglData (C++, Python): void SinFFT (const char *dir)
Функция С: void mgl_data_sinfft (HMDT dat, const char *dir): Do Sine transform of the data in given direction or directions. The Sine transform is \sum a_i \sin(k i).

Метод класса mglData (C++, Python): void CosFFT (const char *dir)
Функция С: void mgl_data_cosfft (HMDT dat, const char *dir): Do Cosine transform of the data in given direction or directions. The Cosine transform is \sum a_i \cos(k i).

Метод класса mglData (C++, Python): void Hankel (const char *dir)
Функция С: void mgl_data_hankel (HMDT dat, const char *dir): Do Hankel transform of the data in given direction or directions. The Hankel transform is \sum a_i J_0(k i).

Метод класса mglData (C++, Python): void Swap (const char *dir)
Функция С: void mgl_data_swap (HMDT dat, const char *dir): Swaps the left and right part of the data in given direction (useful for Fourier spectrum).

Метод класса mglData (C++, Python): void Roll (char dir, num)
Функция С: void mgl_data_roll (HMDT dat, char dir, num): Rolls the data along direction dir. Resulting array will be out[i] = ini[(i+num)%nx] if dir='x'.

Метод класса mglData (C++, Python): void Mirror (const char *dir)
Функция С: void mgl_data_mirror (HMDT dat, const char *dir): Mirror the left-to-right part of the data in given direction. Looks like change the value index i->n-i.

Метод класса mglData (C++, Python): void Sew (const char *dir, float da=2*M_PI)
Функция С: void mgl_data_sew (HMDT dat, const char *dir, float da): Remove value steps (like phase jumps after inverse trigonometric functions) with period da in given direction.

Метод класса mglData (C++, Python): void Smooth (int Type, const char *dir, float delta=0)
Функция С: void mgl_data_smooth (HMDT dat, int Type, float delt, const char *dirs): Smooths the data on specified direction or directions by method Type. Now 4 methods are supported: SMOOTH_NONE does nothing for delta=0 or approaches data to zero with the step delta, SMOOTH_LINE_3 linear averaging by 3 points, SMOOTH_LINE_5 linear averaging by 5 points, SMOOTH_QUAD_5 quadratic averaging by 5 points. Parameter delta forbids to change values of array more than delta from the original ones. String dirs specifies the dimensions which will be smoothed. It may contain characters: ’x’ for 1st dimension, ’y’ for 2nd dimension, ’z’ for 3d dimension.

Метод класса mglData (C++, Python): void Smooth (const char *dir): Smooths the data on specified direction(s). This is the same as Smooth() but argument Type is specified in string as ‘0’ for SMOOTH_NONE, ‘3’ for SMOOTH_LINE_3, ‘5’ for SMOOTH_LINE_5. If string dir don’t contain digits ‘035’ then Type=SMOOTH_QUAD_5 is used.

Метод класса mglData (C++, Python): void Envelop (char dir='x')
Функция С: void mgl_data_envelop (HMDT dat, char dir): Find envelop for data values along direction dir.

Метод класса mglData (C++, Python): void Norm (float v1=0, float v2=1, bool sym=false, int dim=0): Normalizes the data to range [v1,v2]. If flag sym=true then symmetrical interval [-max(|v1|,|v2|), max(|v1|,|v2|)] is used. Modification will be applied only for slices >=dim.

Метод класса mglData (C++, Python): void NormSl (float v1=0, float v2=1, char dir='z', bool keep_en=true, bool sym=false)
Функция С: void mgl_data_norm_slice (HMDT dat, float v1, float v2, char dir, int keep_en, int sym): Normalizes data slice-by-slice along direction dir the data in slices to range [v1,v2]. If flag sym=true then symmetrical interval [-max(|v1|,|v2|), max(|v1|,|v2|)] is used. If keep_en is set then maximal value of k-th slice will be limited by \sqrt\sum a_ij(k)/\sum a_ij(0).

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