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data.table和dplyr软件包在数据操作方面效率的评价 被引量:3
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作者 刘红伟 邓晓伟 +2 位作者 段同庆 李长平 马骏 《中国卫生统计》 CSCD 北大核心 2020年第1期141-144,共4页
目的通过数据验证,比较目前应用广泛、高效的R语言中,data.table软件包和dplyr软件包在数据操作方面的运算效率,为R用户在数据处理效率方面选择合适的软件包提供建议。方法模拟产生不同样本量大小的数据,从选择行列、排序、分组计算、... 目的通过数据验证,比较目前应用广泛、高效的R语言中,data.table软件包和dplyr软件包在数据操作方面的运算效率,为R用户在数据处理效率方面选择合适的软件包提供建议。方法模拟产生不同样本量大小的数据,从选择行列、排序、分组计算、添加更新和合并五个方面比较data.table、dplyr和基本R函数的运算速度。结果data.table在选择行(DT[x==.])、更新、排序、内连接方面运算速度优势明显,在选择行(DT[x<.])、分组计算、左连接、添加方面和dplyr相比没有明显差异,在选择列方面基本R函数最优,data.table表现最差。结论data.table运算效率整体优于dplyr;如果处理数据量在GB级及以上,建议使用data.table软件包,GB级以下,data.table和dplyr两者均可。 展开更多
关键词 R语言 data.table dplyr
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Visualizing Data Tree-Table Based on the Database
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作者 孙广义 侯运炳 +1 位作者 李朝义 张海波 《Journal of China University of Mining and Technology》 2001年第1期56-59,共4页
The data tree table is a type of data structure consisting of data tree and table, which has a wide field of applications. The visual and dynamic growing algorithm of data tree table and its software method are presen... The data tree table is a type of data structure consisting of data tree and table, which has a wide field of applications. The visual and dynamic growing algorithm of data tree table and its software method are presented based on the theory of the data structure and visual technology of software. The method of the expression and management of data tree table with relational mode are explored. 展开更多
关键词 data tree table VISUALIZATION ALGORITHM
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Search Processes in the Exploration of Complex Data under Different Display Conditions
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作者 Charles Tatum David Dickason 《Journal of Data Analysis and Information Processing》 2021年第2期51-62,共12页
The study investigated user experience, display complexity, display type (tables versus graphs), and task difficulty as variables affecting the user’s ability to navigate through complex visual data. A total of 64 pa... The study investigated user experience, display complexity, display type (tables versus graphs), and task difficulty as variables affecting the user’s ability to navigate through complex visual data. A total of 64 participants, 39 undergraduate students (novice users) and 25 graduate students (intermediate-level users) participated in the study. The experimental design was 2 × 2 × 2 × 3 mixed design using two between-subject variables (display complexity, user experience) and two within-subject variables (display format, question difficulty). The results indicated that response time was superior for graphs (relative to tables), especially when the questions were difficult. The intermediate users seemed to adopt more extensive search strategies than novices, as revealed by an analysis of the number of changes they made to the display prior to answering questions. It was concluded that designers of data displays should consider the (a) type of display, (b) difficulty of the task, and (c) expertise level of the user to obtain optimal levels of performance. 展开更多
关键词 Computer Users data Displays data Visualization data tables data Graphs Visual Search data Complexity Visual Displays Visual data
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Mirror Mapping of Laser Interferometer Measurement System on Ultra-precise Movement Stage 被引量:1
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作者 周云飞 于宝成 《Journal of Southwest Jiaotong University(English Edition)》 2006年第4期355-362,共8页
The accuracy and repeatability of the laser interferometer measurement system (LIMS) are often limited by the mirror surface error that comes from the mirror surface shape and distortion. This paper describes a new ... The accuracy and repeatability of the laser interferometer measurement system (LIMS) are often limited by the mirror surface error that comes from the mirror surface shape and distortion. This paper describes a new method to calibrate mirror map on ultraprecise movement stage (UPMS) with nanopositioning and to make a real-time compensation for the mirror surface error by using mirror map data tables with the software algorithm. Based on the mirror map test model, the factors affecting mirror map are analyzed through geometric method on the UPMS with six digrees of freedom. Dam processing methods including spline interpolation and spline offsets are used to process the raw sampling data to build mirror map tables. The linear interpolation as compensation method to make a real-time correction on the stage mirror unflatness is adopted and the correction formulas are illuminated. In this way, the measurement accuracy of the system is obviously improved from 40 nm to 5 nm. 展开更多
关键词 Laser interferometer measurement system (LIMS) Ultra-precise movement stage (UPMS) Mirror mapping Splineinterpolation Mirror map data tables
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A Fast and Memory-Efficient Approach to NDN Name Lookup 被引量:4
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作者 Dacheng He Dafang Zhang +2 位作者 Ke Xu Kun Huang Yanbiao Li 《China Communications》 SCIE CSCD 2017年第10期61-69,共9页
For name-based routing/switching in NDN, the key challenges are to manage large-scale forwarding Tables, to lookup long names of variable lengths, and to deal with frequent updates. Hashing associated with proper leng... For name-based routing/switching in NDN, the key challenges are to manage large-scale forwarding Tables, to lookup long names of variable lengths, and to deal with frequent updates. Hashing associated with proper length-detecting is a straightforward yet efficient solution. Binary search strategy can reduce the number of required hash detecting in the worst case. However, to assure the searching path correct in such a schema, either backtrack searching or redundantly storing some prefixes is required, leading to performance or memory issues as a result. In this paper, we make a deep study on the binary search, and propose a novel mechanism to ensure correct searching path without neither additional backtrack costs nor redundant memory consumptions. Along any binary search path, a bloom filter is employed at each branching point to verify whether a said prefix is present, instead of storing that prefix here. By this means, we can gain significantly optimization on memory efficiency, at the cost of bloom checking before each detecting. Our evaluation experiments on both real-world and randomly synthesized data sets demonstrate our superiorities clearly 展开更多
关键词 named data networking binary search of hash table bloom filter
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A Novel Hybrid Encryption Method Based on Honey Encryption and Advanced DNA Encoding Scheme in Key Generation
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作者 Nwe Ni Khin Thanda Win 《Journal of Computer and Communications》 2022年第9期22-36,共15页
Nowadays, increased information capacity and transmission processes make information security a difficult problem. As a result, most researchers employ encryption and decryption algorithms to enhance information secur... Nowadays, increased information capacity and transmission processes make information security a difficult problem. As a result, most researchers employ encryption and decryption algorithms to enhance information security domains. As it progresses, new encryption methods are being used for information security. In this paper, a hybrid encryption algorithm that combines the honey encryption algorithm and an advanced DNA encoding scheme in key generation is presented. Deoxyribonucleic Acid (DNA) achieves maximal protection and powerful security with high capacity and low modification rate, it is currently being investigated as a potential carrier for information security. Honey Encryption (HE) is an important encryption method for security systems and can strongly prevent brute force attacks. However, the traditional honeyword encryption has a message space limitation problem in the message distribution process. Therefore, we use an improved honey encryption algorithm in our proposed system. By combining the benefits of the DNA-based encoding algorithm with the improved Honey encryption algorithm, a new hybrid method is created in the proposed system. In this paper, five different lookup tables are created in the DNA encoding scheme in key generation. The improved Honey encryption algorithm based on the DNA encoding scheme in key generation is discussed in detail. The passwords are generated as the keys by using the DNA methods based on five different lookup tables, and the disease names are the input messages that are encoded by using the honey encryption process. This hybrid method can reduce the storage overhead problem in the DNA method by applying the five different lookup tables and can reduce time complexity in the existing honey encryption process. 展开更多
关键词 Honey Encryption DNA Encoding Hybrid Method data Lookup tables Time Complexity Storage Overhead
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