tailieunhanh - Niche Modeling: Predictions From Statistical Distributions - Chapter 2

Hệ thống thông tin là sự kết hợp của công nghệ máy tính có thể trợ giúp chúng tôi để lưu trữ, tìm kiếm, và nếu không xử lý các thông tin chúng tôi cần. Trong thực tế, thành phần trung tâm của một hệ thống thông tin là một cơ sở dữ liệu. Tuy nhiên, một cơ sở dữ liệu của chính nó, không đủ cho mô hình thích hợp. Nhiều người dựa vào bảng tính để xử lý dữ liệu của họ. Ngược lại, đối với bộ dữ liệu lớn hơn và đa người dùng cài đặt, các. | Chapter 2 Data Information systems are combinations of computer technologies that help us to store find and otherwise handle the information we need. In practice the central component of an information system is a database. However a database by itself is not enough for niche modeling. Many people rely on spreadsheets for handling their data. In contrast for larger datasets and multi-user installations the conventional approach to information systems is three-tiered consisting of the following a database an analysis system and a presentation system. For example a low-cost system for niche modeling might use a database the statistics language R for analytics and a browser for presentation of results. While there are advantages in partitioning operations in this way inefficiencies and errors are introduced when transferring data between applications particularly in passing data in and out of databases. In keeping with the main theme of this book - successful niche modeling and recognition of sources of error - eliminating a possible source of errors is one of the advantages of a single system like a spreadsheet. Fully integrated systems can also be very efficient. A novel approach developed for the financial industry integrates database and analysis functions into the one memory resident application. The vector-based K language has produced very fast trading applications - over 100 times faster than equivalent three-tiered applications Whi04 . In this section we demonstrate the use of R as a database. While not recommended for large datasets it may be possible to dispense with an external database by replicating relational database operations including select and join in R. As well as simplicity and efficiency for smaller systems a simple database example helps to build knowledge of the R s powerful indexing operations. 23 2007 by Taylor and Francis Group LLC 24 Niche Modeling SQL or structured query language is one of the main languages used in databases. While not