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    从DBSCAN算法谈谈聚类算法

    最近看了一篇关于电子商务防欺诈的相关论文,其中在构建信用卡的个人行为证书中用到了DBSCAN算法。 具体内容请参看论文: Credit card fraud detection: A fusion approach using Dempster–Shafer theory and Bayesian learning。 我就想深入了解下这个聚类方法是怎么工作的。在思考这个具体DBSCAN算法的形成过程中,我还参看了: 1. wikipedia DBSCAN的相关介绍 2. 博文简单易学的机器学习算法——基于密度的聚类算法DBSCAN 3. 论文-A Density-Based Algorithm for Discovering Clusters in Large Spatial Databases with Noise 等相关文献。此篇博文尝试讲清楚”物以类聚,人以群分”这个概念,DBSCAN算法中两个参数的实际物理含义,以及它背后所做的基本假设,由于这方面资料不多,因此都属于个人的猜想,不代表发明DBSCAN算法作者本身的想法,且这也是我正式学习聚类算法中的第一个算法,由于知识的局限性,如有不当,请指正。

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    NC文章详解 | 鼠成纤维细胞单细胞分析发现成纤维细胞在心肌细胞成熟中起关键作用

    Cardiac maturation lays the foundation for postnatal heart development and disease, yet little is known about the contributions of the microenvironment to cardiomyocyte maturation. By integrating single-cell RNA-sequencing data of mouse hearts at multiple postnatal stages, we construct cellular interactomes and regulatory signaling networks. Here we report switching of fibroblast subtypes from a neonatal to adult state and this drives cardiomyocyte maturation. Molecular and functional maturation of neonatal mouse cardiomyocytes and human embryonic stem cell-derived cardiomyocytes are considerably enhanced upon co-culture with corresponding adult cardiac fibroblasts. Further, single-cell analysis of in vivo and in vitro cardiomyocyte maturation trajectories identify highly conserved signaling pathways, pharmacological targeting of which substantially delays cardiomyocyte maturation in postnatal hearts, and markedly enhances cardiomyocyte proliferation and improves cardiac function in infarcted hearts. Together, we identify cardiac fibroblasts as a key constituent in the microenvironment promoting cardiomyocyte maturation, providing insights into how the manipulation of cardiomyocyte maturity may impact on disease development and regeneration.

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    Python数据分析(中英对照)·Introduction to Matplotlib and Pyplot-Matplotlib 和 Pyplot 介绍

    Matplotlib is a Python plotting library that produces publication-quality figures. Matplotlib是一个Python绘图库,用于生成出版物质量的图形。 It can be used both in Python scripts and when using Python’s interactive mode. 它既可以在Python脚本中使用,也可以在使用Python的交互模式时使用。 Matplotlib is a very large library, and getting to know it well takes time. Matplotlib是一个非常大的库,了解它需要时间。 But often we don’t need the full matplotlib library in our programs,and this is where Pyplot comes in handy. 但是我们的程序中通常不需要完整的matplotlib库,这就是Pyplot的用武之地。 Pyplot is a collection of functions that make matplotlib work like Matlab,which you may be familiar with. Pyplot是一组函数,使matplotlib像Matlab一样工作,您可能熟悉这些函数。 Pyplot is especially useful for interactive work,for example, when you’d like to explore a dataset or visually examine your simulation results. Pyplot对于交互式工作尤其有用,例如,当您希望浏览数据集或直观地检查模拟结果时。 We’ll be using Pyplot in all our data visualizations. 我们将在所有数据可视化中使用Pyplot。 Pyplot provides what is sometimes called a state machine interface to matplotlib library. Pyplot为matplotlib库提供了有时称为状态机的接口。 You can loosely think of it as a process where you create figures one at a time,and all commands affect the current figure and the current plot. 您可以粗略地将其视为一个一次创建一个地物的过程,所有命令都会影响当前地物和当前绘图。 We will mostly use NumPy arrays for storing the data that we’d like to plot, but we’ll occasionally use other types of data objects such as built-in lists. 我们将主要使用NumPy数组来存储要绘制的数据,但偶尔也会使用其他类型的数据对象,如内置列表。 As you may have realized, saying matplotlib.pyplot is kind of a mouthful, and it’s a lot to type too. 正如您可能已经意识到的那样,说matplotlib.pyplot有点口齿不清,而且打字也很费劲。 That’s why virtually everyone who uses the library imports it as plt, which is a lot shorter. 这就是为什么几乎所有使用该库的人都将其作为plt导入,而plt要短得多。 So to import the library, we will type the following– import matplotlib.pyplot as plt. 因此,要导入库,我们将键入以下内容–import matplotlib.pyplot as plt。 Now we are ready to start our plotting. 现在我们准备开始我们的阴谋。 A basis but very useful command is the plt plot function, which can be used to plot lines and markers. plt plot函数是一个基本

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