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# CS代写|机器学习代写Machine Learning代考|COMP4702 Performance Measure

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## CS代写|机器学习代写Machine Learning代考|Performance Measure

In order to evaluate the generalization ability of models, we need not only practical and effective estimation methods but also some performance measures that can quantify the generalization ability. Different performance measures reflect the varied demands of tasks and produce different evaluation results. In other words, the quality of a model is a relative concept that depends on the algorithm and data as well as the task requirement.

In prediction problems, we are given a data set $D=$ $\left{\left(\boldsymbol{x}1, y_1\right),\left(\boldsymbol{x}_2, y_2\right), \ldots,\left(\boldsymbol{x}_m, y_m\right)\right}$, where $y_i$ is the ground-truth label of the sample $\boldsymbol{x}_i$. To evaluate the performance of a learner $f$, we compare its prediction $f(\boldsymbol{x})$ to the ground-truth label $y$. For regression problems, the most commonly used performance measure is the Mean Squared Error (MSE): $$E(f ; D)=\frac{1}{m} \sum{i=1}^m\left(f\left(\boldsymbol{x}i\right)-y_i\right)^2 .$$ More generally, for a data distribution $\mathcal{D}$ and a probability density function $p(\cdot)$, the MSE is written as $$E(f ; \mathcal{D})=\int{\boldsymbol{x} \sim D}(f(\boldsymbol{x})-y)^2 p(\boldsymbol{x}) d \boldsymbol{x} .$$
The rest of this section will introduce some common performance measures for classification problems.

## CS代写|机器学习代写Machine Learning代考|Error Rate and Accuracy

At the beginning of this chapter, we discussed error rate and accuracy, which are the most commonly used performance measures in classification problems, including both binary classification and multiclass classification. Error rate is the proportion of misclassified samples to all samples, whereas accuracy is the proportion of correctly classified samples instead. Given a data set $D$, we define error rate as
$$E(f ; D)=\frac{1}{m} \sum_{i=1}^m \mathbb{I}\left(f\left(\boldsymbol{x}i\right) \neq y_i\right)$$ and accuracy as \begin{aligned} \operatorname{acc}(f ; D) &=\frac{1}{m} \sum{i=1}^m \mathbb{I}\left(f\left(\boldsymbol{x}i\right)=y_i\right) \ &=1-E(f ; D) . \end{aligned} More generally, for a data distribution $\mathcal{D}$ and a probability density function $p(\cdot)$, error rate and accuracy can be, respectively, written as \begin{aligned} E(f ; \mathcal{D}) &=\int{\boldsymbol{x} \sim D} \mathbb{I}(f(\boldsymbol{x}) \neq y) p(\boldsymbol{x}) d \boldsymbol{x}, \ \operatorname{acc}(f ; \mathcal{D}) &=\int_{\boldsymbol{x} \sim D} \mathbb{I}(f(\boldsymbol{x})=y) p(\boldsymbol{x}) d \boldsymbol{x} \ &=1-E(f ; \mathcal{D}) . \end{aligned}

## CS代写|机器学习代写Machine Learning代考|Performance Measure

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## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。