diff --git a/lib/node_modules/@stdlib/stats/base/ndarray/scovarmtk/README.md b/lib/node_modules/@stdlib/stats/base/ndarray/scovarmtk/README.md index dbe0cdd9c9dc..78e480192f76 100644 --- a/lib/node_modules/@stdlib/stats/base/ndarray/scovarmtk/README.md +++ b/lib/node_modules/@stdlib/stats/base/ndarray/scovarmtk/README.md @@ -186,6 +186,219 @@ console.log( v ); + + +* * * + +
+ +## C APIs + + + +
+ +
+ + + + + +
+ +### Usage + +```c +#include "stdlib/stats/base/ndarray/scovarmtk.h" +``` + +#### stdlib_stats_scovarmtk( arrays ) + +Computes the covariance of two one-dimensional single-precision floating-point ndarrays provided known means and using a one-pass textbook algorithm. + +```c +#include "stdlib/ndarray/ctor.h" +#include "stdlib/ndarray/dtypes.h" +#include "stdlib/ndarray/index_modes.h" +#include "stdlib/ndarray/orders.h" +#include "stdlib/ndarray/base/bytes_per_element.h" +#include + +// Create input ndarrays: +const float xdata[] = { 1.0f, -2.0f, 2.0f }; +const float ydata[] = { 2.0f, -2.0f, 1.0f }; +int64_t shape[] = { 3 }; +int64_t strides[] = { STDLIB_NDARRAY_FLOAT32_BYTES_PER_ELEMENT }; +int8_t submodes[] = { STDLIB_NDARRAY_INDEX_ERROR }; + +struct ndarray *x = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)xdata, 1, shape, strides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes ); +struct ndarray *y = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)ydata, 1, shape, strides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes ); + +// Create an ndarray for specifying the degrees of freedom adjustment: +const float cdata[] = { 1.0f }; +int64_t cstrides[] = { 0 }; +struct ndarray *corr = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)cdata, 0, NULL, cstrides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes ); + +// Create ndarrays for specifying the known means: +const float mxdata[] = { 1.0f/3.0f }; +const float mydata[] = { 1.0f/3.0f }; +struct ndarray *meanx = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)mxdata, 0, NULL, cstrides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes ); +struct ndarray *meany = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)mydata, 0, NULL, cstrides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes ); + +// Compute the result: +const struct ndarray *arrays[] = { x, y, corr, meanx, meany }; +float v = stdlib_stats_scovarmtk( arrays ); +// returns ~3.8333f + +// Free allocated memory: +stdlib_ndarray_free( x ); +stdlib_ndarray_free( y ); +stdlib_ndarray_free( corr ); +stdlib_ndarray_free( meanx ); +stdlib_ndarray_free( meany ); +``` + +The function accepts the following arguments: + +- **arrays**: `[in] struct ndarray**` list containing the following ndarrays: + + - `[in] struct ndarray*` first one-dimensional input ndarray. + - `[in] struct ndarray*` second one-dimensional input ndarray. + - `[in] struct ndarray*` a zero-dimensional ndarray specifying the degrees of freedom adjustment. Setting this parameter to a value other than `0` has the effect of adjusting the divisor during the calculation of the [covariance][covariance] according to `N-c` where `c` corresponds to the provided degrees of freedom adjustment and `N` corresponds to the number of elements in each input ndarray. When computing the population [covariance][covariance], setting this parameter to `0` is the standard choice (i.e., the provided arrays contain data constituting entire populations). When computing the unbiased sample [covariance][covariance], setting this parameter to `1` is the standard choice (i.e., the provided arrays contain data sampled from larger populations; this is commonly referred to as Bessel's correction). + - `[in] struct ndarray*` a zero-dimensional ndarray specifying the mean of the first one-dimensional ndarray. + - `[in] struct ndarray*` a zero-dimensional ndarray specifying the mean of the second one-dimensional ndarray. + +```c +float stdlib_stats_scovarmtk( const struct ndarray *arrays[] ); +``` + +
+ + + + + +
+ +
+ + + + + +
+ +### Examples + +```c +#include "stdlib/stats/base/ndarray/scovarmtk.h" +#include "stdlib/ndarray/ctor.h" +#include "stdlib/ndarray/dtypes.h" +#include "stdlib/ndarray/index_modes.h" +#include "stdlib/ndarray/orders.h" +#include "stdlib/ndarray/base/bytes_per_element.h" +#include +#include +#include + +int main( void ) { + // Create data buffers: + const float xdata[] = { 1.0f, -2.0f, 3.0f, -4.0f, 5.0f, -6.0f, 7.0f, -8.0f }; + const float ydata[] = { 2.0f, -1.0f, 1.0f, -3.0f, 3.0f, -5.0f, 5.0f, -7.0f }; + + // Specify the number of array dimensions: + const int64_t ndims = 1; + + // Specify the array shape: + int64_t shape[] = { 4 }; + + // Specify the array strides: + int64_t strides[] = { 2 * STDLIB_NDARRAY_FLOAT32_BYTES_PER_ELEMENT }; + + // Specify the byte offset: + const int64_t offset = 0; + + // Specify the array order: + const enum STDLIB_NDARRAY_ORDER order = STDLIB_NDARRAY_ROW_MAJOR; + + // Specify the index mode: + const enum STDLIB_NDARRAY_INDEX_MODE imode = STDLIB_NDARRAY_INDEX_ERROR; + + // Specify the subscript index modes: + int8_t submodes[] = { STDLIB_NDARRAY_INDEX_ERROR }; + const int64_t nsubmodes = 1; + + // Create the first input ndarray: + struct ndarray *x = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)xdata, ndims, shape, strides, offset, order, imode, nsubmodes, submodes ); + if ( x == NULL ) { + fprintf( stderr, "Error allocating memory.\n" ); + exit( 1 ); + } + + // Create the second input ndarray: + struct ndarray *y = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)ydata, ndims, shape, strides, offset, order, imode, nsubmodes, submodes ); + if ( y == NULL ) { + fprintf( stderr, "Error allocating memory.\n" ); + exit( 1 ); + } + + // Create a data buffer for an ndarray specifying the degrees of freedom adjustment: + const float cdata[] = { 1.0f }; + + // Create data buffers for ndarrays specifying the means of the input ndarrays: + const float mxdata[] = { 4.0f }; + const float mydata[] = { 2.75f }; + + // Specify the array strides for zero-dimensional ndarrays: + int64_t cstrides[] = { 0 }; + + // Create an ndarray for the degrees of freedom adjustment: + struct ndarray *corr = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)cdata, 0, NULL, cstrides, 0, order, imode, nsubmodes, submodes ); + if ( corr == NULL ) { + fprintf( stderr, "Error allocating memory.\n" ); + exit( 1 ); + } + + // Create an ndarray for the mean of the first input ndarray: + struct ndarray *meanx = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)mxdata, 0, NULL, cstrides, 0, order, imode, nsubmodes, submodes ); + if ( meanx == NULL ) { + fprintf( stderr, "Error allocating memory.\n" ); + exit( 1 ); + } + + // Create an ndarray for the mean of the second input ndarray: + struct ndarray *meany = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)mydata, 0, NULL, cstrides, 0, order, imode, nsubmodes, submodes ); + if ( meany == NULL ) { + fprintf( stderr, "Error allocating memory.\n" ); + exit( 1 ); + } + + // Define a list of ndarrays: + const struct ndarray *arrays[] = { x, y, corr, meanx, meany }; + + // Compute the result: + float v = stdlib_stats_scovarmtk( arrays ); + + // Print the result: + printf( "result: %f\n", v ); + + // Free allocated memory: + stdlib_ndarray_free( x ); + stdlib_ndarray_free( y ); + stdlib_ndarray_free( corr ); + stdlib_ndarray_free( meanx ); + stdlib_ndarray_free( meany ); +} +``` + +
+ + + +
+ + +