feat: add Wald distribution PDF

lib/node_modules/@stdlib/stats/base/dists/wald/pdf/binding.gyp

@@ -0,0 +1,170 @@
+# @license Apache-2.0
+#
+# Copyright (c) 2025 The Stdlib Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# A `.gyp` file for building a Node.js native add-on.
+#
+# [1]: https://gyp.gsrc.io/docs/InputFormatReference.md
+# [2]: https://gyp.gsrc.io/docs/UserDocumentation.md
+{
+  # List of files to include in this file:
+  'includes': [
+    './include.gypi',
+  ],
+
+  # Define variables to be used throughout the configuration for all targets:
+  'variables': {
+    # Target name should match the add-on export name:
+    'addon_target_name%': 'addon',
+
+    # Set variables based on the host OS:
+    'conditions': [
+      [
+        'OS=="win"',
+        {
+          # Define the object file suffix:
+          'obj': 'obj',
+        },
+        {
+          # Define the object file suffix:
+          'obj': 'o',
+        }
+      ], # end condition (OS=="win")
+    ], # end conditions
+  }, # end variables
+
+  # Define compile targets:
+  'targets': [
+
+    # Target to generate an add-on:
+    {
+      # The target name should match the add-on export name:
+      'target_name': '<(addon_target_name)',
+
+      # Define dependencies:
+      'dependencies': [],
+
+      # Define directories which contain relevant include headers:
+      'include_dirs': [
+        # Local include directory:
+        '<@(include_dirs)',
+      ],
+
+      # List of source files:
+      'sources': [
+        '<@(src_files)',
+      ],
+
+      # Settings which should be applied when a target's object files are used as linker input:
+      'link_settings': {
+        # Define libraries:
+        'libraries': [
+          '<@(libraries)',
+        ],
+
+        # Define library directories:
+        'library_dirs': [
+          '<@(library_dirs)',
+        ],
+      },
+
+      # C/C++ compiler flags:
+      'cflags': [
+        # Enable commonly used warning options:
+        '-Wall',
+
+        # Aggressive optimization:
+        '-O3',
+      ],
+
+      # C specific compiler flags:
+      'cflags_c': [
+        # Specify the C standard to which a program is expected to conform:
+        '-std=c99',
+      ],
+
+      # C++ specific compiler flags:
+      'cflags_cpp': [
+        # Specify the C++ standard to which a program is expected to conform:
+        '-std=c++11',
+      ],
+
+      # Linker flags:
+      'ldflags': [],
+
+      # Apply conditions based on the host OS:
+      'conditions': [
+        [
+          'OS=="mac"',
+          {
+            # Linker flags:
+            'ldflags': [
+              '-undefined dynamic_lookup',
+              '-Wl,-no-pie',
+              '-Wl,-search_paths_first',
+            ],
+          },
+        ], # end condition (OS=="mac")
+        [
+          'OS!="win"',
+          {
+            # C/C++ flags:
+            'cflags': [
+              # Generate platform-independent code:
+              '-fPIC',
+            ],
+          },
+        ], # end condition (OS!="win")
+      ], # end conditions
+    }, # end target <(addon_target_name)
+
+    # Target to copy a generated add-on to a standard location:
+    {
+      'target_name': 'copy_addon',
+
+      # Declare that the output of this target is not linked:
+      'type': 'none',
+
+      # Define dependencies:
+      'dependencies': [
+        # Require that the add-on be generated before building this target:
+        '<(addon_target_name)',
+      ],
+
+      # Define a list of actions:
+      'actions': [
+        {
+          'action_name': 'copy_addon',
+          'message': 'Copying addon...',
+
+          # Explicitly list the inputs in the command-line invocation below:
+          'inputs': [],
+
+          # Declare the expected outputs:
+          'outputs': [
+            '<(addon_output_dir)/<(addon_target_name).node',
+          ],
+
+          # Define the command-line invocation:
+          'action': [
+            'cp',
+            '<(PRODUCT_DIR)/<(addon_target_name).node',
+            '<(addon_output_dir)/<(addon_target_name).node',
+          ],
+        },
+      ], # end actions
+    }, # end target copy_addon
+  ], # end targets
+}

lib/node_modules/@stdlib/stats/base/dists/wald/pdf/docs/repl.txt

@@ -0,0 +1,87 @@
+{{alias}}( x, μ, λ )
+    Evaluates the probability density function (PDF) for a Wald distribution
+    with mean `μ` and shape parameter `λ` at a value `x`.
+
+    If provided `NaN` as any argument, the function returns `NaN`.
+
+    If provided `μ <= 0` or `λ < 0`, the function returns `NaN`.
+
+    Parameters
+    ----------
+    x: number
+        Input value.
+
+    μ: number
+        Mean parameter.
+
+    λ: number
+        Shape parameter.
+
+    Returns
+    -------
+    out: number
+        Evaluated PDF.
+
+    Examples
+    --------
+    > var y = {{alias}}( 2.0, 1.0, 1.0 )
+    ~0.110
+    > y = {{alias}}( 5.0, 3.0, 2.0 )
+    ~0.046
+    > y = {{alias}}( NaN, 1.0, 1.0 )
+    NaN
+    > y = {{alias}}( 2.0, NaN, 1.0 )
+    NaN
+    > y = {{alias}}( 2.0, 1.0, NaN )
+    NaN
+
+    // Non-positive mean:
+    > y = {{alias}}( 2.0, 0.0, 1.0 )
+    NaN
+    > y = {{alias}}( 2.0, -1.0, 1.0 )
+    NaN
+
+    // Negative shape parameter:
+    > y = {{alias}}( 2.0, 1.0, -1.0 )
+    NaN
+
+    // Degenerate distribution when `λ = 0.0`:
+    > y = {{alias}}( 2.0, 1.0, 0.0 )
+    0.0
+    > y = {{alias}}( 1.0, 1.0, 0.0 )
+    infinity
+
+    // Outside support (x <= 0):
+    > y = {{alias}}( 0.0, 1.0, 1.0 )
+    0.0
+    > y = {{alias}}( -1.0, 1.0, 1.0 )
+    0.0
+
+
+{{alias}}.factory( μ, λ )
+    Returns a function for evaluating the probability density function (PDF) of
+    a Wald distribution with mean `μ` and shape parameter `λ`.
+
+    Parameters
+    ----------
+    μ: number
+        Mean parameter.
+
+    λ: number
+        Shape parameter.
+
+    Returns
+    -------
+    pdf: Function
+        Probability density function (PDF).
+
+    Examples
+    --------
+    > var myPDF = {{alias}}.factory( 3.0, 2.0 );
+    > var y = myPDF( 2.0 )
+    ~0.189
+    > y = myPDF( 5.0 )
+    ~0.046
+
+    See Also
+    --------

lib/node_modules/@stdlib/stats/base/dists/wald/pdf/docs/types/index.d.ts

@@ -0,0 +1,124 @@
+/*
+* @license Apache-2.0
+*
+* Copyright (c) 2025 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+// TypeScript Version: 4.1
+
+/**
+* Evaluates the probability density function (PDF) for a Wald distribution.
+*
+* @param x - input value
+* @returns evaluated PDF
+*/
+type Unary = ( x: number ) => number;
+
+/**
+* Interface for the probability density function (PDF) of a Wald distribution.
+*/
+interface PDF {
+	/**
+	* Evaluates the probability density function (PDF) for a Wald distribution with mean `mu` and shape parameter `lambda` at a value `x`.
+	*
+	* ## Notes
+	*
+	* -   If provided `mu <= 0` or `lambda < 0`, the function returns `NaN`.
+	*
+	* @param x - input value
+	* @param mu - mean parameter
+	* @param lambda - shape parameter
+	* @returns evaluated probability density function
+	*
+	* @example
+	* var y = pdf( 2.0, 1.0, 1.0 );
+	* // returns ~0.110
+	*
+	* @example
+	* var y = pdf( 5.0, 3.0, 2.0 );
+	* // returns ~0.046
+	*
+	* @example
+	* var y = pdf( NaN, 1.0, 1.0 );
+	* // returns NaN
+	*
+	* @example
+	* var y = pdf( 2.0, NaN, 1.0 );
+	* // returns NaN
+	*
+	* @example
+	* var y = pdf( 2.0, 1.0, NaN );
+	* // returns NaN
+	*
+	* @example
+	* // Non-positive mean:
+	* var y = pdf( 2.0, 0.0, 1.0 );
+	* // returns NaN
+	*
+	* @example
+	* // Negative shape parameter:
+	* var y = pdf( 2.0, 1.0, -1.0 );
+	* // returns NaN
+	*
+	* @example
+	* var y = pdf( 2.0, 1.0, 0.0 );
+	* // returns 0.0
+	*
+	* @example
+	* var y = pdf( 1.0, 1.0, 0.0 );
+	* // returns Infinity
+	*/
+	( x: number, mu: number, lambda: number ): number;
+
+	/**
+	* Returns a function for evaluating the probability density function (PDF) for a Wald distribution.
+	*
+	* @param mu - mean parameter
+	* @param lambda - shape parameter
+	* @returns function to evaluate the probability density function
+	*
+	* @example
+	* var myPDF = pdf.factory( 3.0, 2.0 );
+	* var y = myPDF( 2.0 );
+	* // returns ~0.189
+	*
+	* y = myPDF( 5.0 );
+	* // returns ~0.046
+	*/
+	factory( mu: number, lambda: number ): Unary;
+}
+
+/**
+* Wald distribution probability density function (PDF).
+*
+* @param x - input value
+* @param mu - mean parameter
+* @param lambda - shape parameter
+* @returns evaluated PDF
+*
+* @example
+* var y = pdf( 2.0, 1.0, 1.0 );
+* // returns ~0.110
+*
+* var myPDF = pdf.factory( 3.0, 2.0 );
+* y = myPDF( 2.0 );
+* // returns ~0.189
+*/
+declare var pdf: PDF;
+
+
+// EXPORTS //
+
+export = pdf;