simple knn
时间: 2024-08-14 15:08:18 浏览: 588
简单K近邻(Simple K-Nearest Neighbors,简称KNN)是一种基于实例的学习(Instance-based Learning)算法,它主要用于分类和回归分析。KNN的基本思想是,给定一个新的数据点,通过计算它与训练集中所有样本之间的距离(通常使用欧几里得距离),找出与其最近的K个邻居,然后根据这K个邻居的标签(对于分类任务)或值(对于回归任务)来预测新数据点的结果。
步骤如下:
1. 训练阶段:将数据集划分为训练集,其中包含已知类别或属性值的样本。
2. 预测阶段:对于新的未知样本,计算其与训练集中每个样本的距离,并选取K个最相似的样本。
3. 决策:根据K个邻居中的大多数类别(分类任务)或取平均值(回归任务)作为预测结果。
KNN算法非常直观简单,但是它的缺点也很明显,如对大量存储空间的需求较高,因为需要存储整个训练集;而且对于大规模数据集,由于计算量大,不适合实时处理。此外,如果特征维度高(即“维度灾难”),可能会导致性能下降。
相关问题
(3dgs) PS E:\wg\gaussian-splatting\submodules\simple-knn\simple-knn-main> pip install . Processing e:\wg\gaussian-splatting\submodules\simple-knn\simple-knn-main Preparing metadata (setup.py) ... done Building wheels for collected packages: simple_knn pep517` option, (possibly combined with `--no-build-isolation`), or adding a `pyproject.toml` file to the source tree of 'simple_knn'. Discussion can be found at https://github.com/pypa/pip/issues/6334 Building wheel for simple_knn (setup.py) ... error error: subprocess-exited-with-error × python setup.py bdist_wheel did not run successfully. │ exit code: 1 ╰─> [4 lines of output] running bdist_wheel running build running build_ext error: [WinError 2] 系统找不到指定的文件。 [end of output] note: This error originates from a subprocess, and is likely not a problem with pip. ERROR: Failed building wheel for simple_knn Running setup.py clean for simple_knn Failed to build simple_knn ERROR: Failed to build installable wheels for some pyproject.toml based projects (simple_knn) standards-based tools. See https://github.com/pypa/setuptools/issues/917 for details. ******************************************************************************** !! self.initialize_options() running bdist_egg running egg_info writing simple_knn.egg-info\PKG-INFO writing dependency_links to simple_knn.egg-info\dependency_links.txt writing top-level names to simple_knn.egg-info\top_level.txt reading manifest file 'simple_knn.egg-info\SOURCES.txt' adding license file 'LICENSE.md' writing manifest file 'simple_knn.egg-info\SOURCES.txt' installing library code to build\bdist.win-amd64\egg running install_lib running build_ext error: [WinError 2] 系统找不到指定的文件。
在 Windows 环境下安装 `simple_knn` 模块时遇到构建错误,提示 `[WinError 2] 系统找不到指定的文件`,通常是由于缺少必要的编译依赖或环境配置不当所致。以下是一些可能的解决方法:
### 检查 Python 和 pip 版本
确保使用的 Python 和 pip 是目标虚拟环境中的版本,并且与当前系统兼容。可以通过以下命令检查:
```bash
python --version
pip --version
```
### 安装 Microsoft Visual C++ Build Tools
Windows 上的一些 Python 扩展模块需要 Microsoft Visual C++ 编译工具链支持。如果未正确安装这些工具,可能导致无法找到相关依赖文件。建议下载并安装 [Microsoft Visual C++ Build Tools](https://visualstudio.microsoft.com/visual-cpp-build-tools/)。
### 使用预编译 wheel 文件
某些第三方库为 Windows 提供了预编译的 `.whl` 文件,可以避免从源码编译带来的问题。尝试通过以下方式安装:
1. 访问 [Unofficial Windows Binaries for Python Extension Packages](https://www.lfd.uci.edu/~gohlke/pythonlibs/)。
2. 搜索 `simple_knn` 或其依赖项(如 PyTorch 相关包)。
3. 下载匹配当前 Python 版本和架构(32位/64位)的 wheel 文件。
4. 使用 pip 安装该 wheel 文件:
```bash
pip install path_to_downloaded_wheel.whl
```
### 升级 setuptools 和 pip
有时旧版本的 `setuptools` 或 `pip` 可能导致安装失败。升级到最新版本可能会解决问题:
```bash
pip install --upgrade pip setuptools
```
### 安装 CUDA Toolkit(若使用 GPU)
如果安装的是依赖于 CUDA 的模块,则需确保已安装对应版本的 CUDA Toolkit,并且环境变量配置正确。可以从 [NVIDIA 官方网站](https://developer.nvidia.com/cuda-downloads) 获取合适的版本。
### 配置环境变量
确认所有相关的开发工具路径(如 Visual Studio、CUDA 等)都已正确添加至系统环境变量中。例如,确保 `cl.exe`(MSVC 编译器)位于系统 PATH 中。
### 使用 Conda 环境
Conda 能更好地管理依赖关系,尤其是对于涉及本地库的复杂项目。可以尝试创建一个新的 conda 环境并安装所需的包:
```bash
conda create -n simpleknn_env python=3.x
conda activate simpleknn_env
# 如果有可用的 conda 包,可以直接安装
conda install -c conda-forge simple_knn
# 否则使用 pip 安装
pip install simple_knn
```
### 清理缓存并重新安装
有时 pip 缓存可能导致问题,清理缓存后重试可能有效:
```bash
pip cache purge
pip install --no-cache-dir simple_knn
```
### 查看完整错误日志
详细阅读完整的错误输出,特别是靠近错误信息顶部的部分,通常会指出具体缺失哪个文件或依赖项,从而帮助定位问题根源。
### 示例:手动指定编译器路径(可选)
如果确定编译器存在但未被识别,可以在安装前手动设置编译器路径:
```bash
set VSINSTALLDIR="C:\Program Files (x86)\Microsoft Visual Studio\2019\Community"
set VCINSTALLDIR=%VSINSTALLDIR%\VC
set PATH=%VCINSTALLDIR%\bin\hostx86\x86;%PATH%
```
---
simple-knn
### Simple KNN Algorithm Implementation and Explanation
K-nearest neighbors (KNN) is one of the simplest yet effective algorithms for both classification and regression problems. In its essence, KNN operates based on similarity measures between instances.
#### How KNN Works
For any new instance requiring prediction, KNN finds the most similar k training samples within the dataset according to some distance metric such as Euclidean distance. For classification tasks, the majority class among those nearest neighbors determines the predicted label; while for regression tasks, predictions might take the average value of target variables from these closest points[^1].
#### Implementing Simple KNN in Python
Below demonstrates how to implement a simple version of the KNN classifier using Python:
```python
import numpy as np
from collections import Counter
from sklearn.model_selection import train_test_split
from sklearn.datasets import load_iris
def euclidean_distance(x1, x2):
return np.sqrt(np.sum((x1 - x2)**2))
class SimpleKNN:
def __init__(self, k=3):
self.k = k
def fit(self, X_train, y_train):
self.X_train = X_train
self.y_train = y_train
def predict(self, X_test):
predictions = [self._predict(x) for x in X_test]
return np.array(predictions)
def _predict(self, x):
distances = [euclidean_distance(x, x_train) for x_train in self.X_train]
k_indices = np.argsort(distances)[:self.k]
k_nearest_labels = [self.y_train[i] for i in k_indices]
most_common = Counter(k_nearest_labels).most_common(1)
return most_common[0][0]
# Load iris dataset
data = load_iris()
X, y = data.data, data.target
# Splitting into training/testing sets
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)
# Initialize our custom knn model
clf = SimpleKNN(k=3)
clf.fit(X_train, y_train)
# Predictions
predictions = clf.predict(X_test)
print(f"Predicted labels: {predictions}")
```
This code snippet defines `SimpleKNN`, which implements basic functionalities including fitting models with given datasets (`fit` method), predicting unseen sample classes (`predict` method), calculating pairwise distances via helper function `_predict`. Moreover, this example uses Iris flower species recognition task provided by Scikit-Learn library as demonstration purpose only[^4].
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